Method and apparatus for transmitting and receiving demodulation reference signal

ABSTRACT

Methods, apparatuses, and systems described herein generally relate to a reference signal generation and mapping. For example, a method comprises determining a first set of antenna ports for a demodulation reference signal (DM-RS) transmission; determining, based on the first set, a frequency index associated with four adjacent resource elements, wherein the four adjacent resource elements correspond to two adjacent symbols in a time axis and to two adjacent subcarriers in a frequency axis; generating, based on a first orthogonal cover code and a second orthogonal cover code, a DM-RS associated with the first set of antenna ports; and transmitting, via a mapping to the four adjacent resource elements, the DM-RS associated with the first set of antenna ports.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from and the benefit of Korean PatentApplication Nos. 10-2017-0037049, filed on Mar. 23, 2017,10-2017-0101597, filed on Aug. 10, 2017, and 10-2017-0153553, filed onNov. 17, 2017, each of which is hereby incorporated by reference in itsentirety.

BACKGROUND 1. Field

The present disclosure relates to a wireless communication system, andparticularly, to a method and apparatus for transmitting and receiving areference signal.

2. Discussion of the Background

The IMT(International Mobile Telecommunication) frameworks and standardshave been developed by ITU(International Telecommunication Union) and,recently, the 5^(th) generation (5G) communication has been discussedthrough a program called “IMT for 2020 and beyond”.

In order to satisfy requirements from “IMT for 2020 and beyond”, thediscussion is in progress about a way for enabling the 3rd GenerationPartnership Project (3GPP) New Radio (NR) system to support variousnumerologies by taking into consideration various scenarios, variousservice requirements, potential system compatibility, or the like.

However, a method of configuring a pattern for a Demodulation Referencesignal (DMRS) that supports an increased number of layers, an increasednumber of antenna ports, and Multi User-Multiple Input Multiple Output(MU-MIMO) for terminals in various operation modes in the NR system, anda method of signaling pattern configuration information have not yetbeen defined.

SUMMARY

An aspect of the present disclosure is to provide a method and apparatusfor signaling pattern configuration information of a demodulationreference signal, which supports an increased number of layers and anincreased number of antenna ports.

Another aspect of the present disclosure is to provide a method andapparatus for dynamically signaling pattern configuration information ofa demodulation reference signal based on signaling set candidates ofdemodulation reference signal configuration.

An example method comprises determining a first set of antenna ports fora demodulation reference signal (DM-RS) transmission; determining, basedon the first set, a frequency index associated with four adjacentresource elements, wherein the four adjacent resource elementscorrespond to two adjacent symbols in a time axis and to two adjacentsubcarriers in a frequency axis; generating, based on a first orthogonalcover code and a second orthogonal cover code, a DM-RS associated withthe first set of antenna ports; and transmitting, via a mapping to thefour adjacent resource elements, the DM-RS associated with the first setof antenna ports.

Another example method comprises determining, by a base station, a typeof demodulation reference signal (DM-RS) configuration; determining twoadjacent orthogonal frequency division multiplexing (OFDM) symbols formapping DM-RSs for at least three code division multiplexing (CDM)groups; determining a first set of antenna ports for a demodulationreference signal (DM-RS) transmission to a first user equipment (UE),wherein a first CDM group, among the at least three CDM groups,comprises the first set of antenna ports; determining, based on thefirst set, a frequency index associated with first four adjacentresource elements, wherein the first four adjacent resource elementscorrespond to the two adjacent OFDM symbols in a time axis and to firsttwo adjacent subcarriers in a frequency axis; and mapping, based on afirst orthogonal cover code and a second orthogonal cover code, a firstDM-RS to the first four adjacent resource elements, wherein the firstDM-RS is associated with the first set of antenna ports.

Another example method comprises receiving, by a user equipment (UE) andfrom a base station, a type of demodulation reference signal (DM-RS)configuration, a first set of antenna ports for a DM-RS transmissionfrom the UE, and information indicating a quantity of code divisionmultiplexing (CDM) groups scheduled for a DM-RS transmission;determining two adjacent symbols for mapping a DM-RS; determining, basedon the first set, a frequency index associated with first four adjacentresource elements, wherein the first four adjacent resource elementscorrespond to the two adjacent symbols in a time axis and to first twoadjacent subcarriers in a frequency axis; generating, based on a firstorthogonal cover code and a second orthogonal cover code, a DM-RSassociated with the first set of antenna ports; and transmitting, via amapping to the first four adjacent resource elements, the DM-RSassociated with the first set of antenna ports.

This Summary is submitted with the understanding that it will not beused to interpret or limit the scope or meaning of the claims. ThisSummary is not intended to identify key features or essential featuresof the claimed subject matter, nor is it intended to be used as an aidin determining the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating examples of a Demodulation ReferenceSignal (DMRS) pattern according to the present disclosure;

FIG. 2 is a diagram illustrating additional examples of a DMRS patternaccording to the present disclosure;

FIGS. 3 to 10 are diagrams illustrating various examples of a DMRSpattern in one PRB according to the present disclosure;

FIG. 11 is a diagram illustrating a method of signaling DMRS patternconfiguration information according to the present disclosure; and

FIG. 12 is a diagram illustrating the configurations of a base stationdevice and a terminal device according to the present disclosure.

FIGS. 13 to 16 are views showing examples of a DMRS pattern to which thepresent invention may be applied.

FIG. 17 is a view showing an application example of a TD-OCC and aFD-OCC to which the present invention may be applied.

FIG. 18 is a view showing a flowchart illustrating a method oftransmitting and receiving a downlink DMRS according to the presentdisclosure.

FIG. 19 is a view showing a flowchart illustrating a method oftransmitting and receiving an uplink DMRS according to the presentdisclosure.

FIG. 20 is a view showing a configuration of a wireless device accordingto the present disclosure.

FIG. 21 is a view showing a wireless communication system to which thepresent invention is applied.

FIG. 22 is a view showing a DMRS pattern when a first DMRS configurationtype is applied and one symbol is used for a DMRS.

FIG. 23 is a view showing a DMRS pattern when a first DMRS configurationtype is applied and two symbols are used for a DMRS.

FIG. 24 is a view showing a DMRS pattern when a second DMRSconfiguration type is applied and one symbol is used for a DMRS.

FIG. 25 is a view showing a DMRS pattern when a second DMRSconfiguration type is applied and two symbols are used for a DMRS.

FIG. 26 is a view showing a mapping example of an OCC which is appliedto the present invention.

FIG. 27 is a view showing a method of transmitting a downlink DMRS in anembodiment of the present invention.

FIG. 28 is a view showing a method of transmitting an uplink DMRS in anembodiment of the present invention.

FIG. 29 is a showing a block diagram of a wireless communication systemaccording to an embodiment of the present invention.

DETAILED DESCRIPTION

Various examples will be described more fully hereinafter with referenceto the accompanying drawings. Throughout the drawings and the detaileddescription, unless otherwise described, the same drawing referencenumerals are understood to refer to the same elements, features, andstructures. In describing the examples, detailed description on knownconfigurations or functions may be omitted for clarity and conciseness.

Further, the terms, such as first, second, A, B, (a), (b), and the likemay be used herein to describe elements in the description herein. Theterms are used to distinguish one element from another element. Thus,the terms do not limit the element, an arrangement order, a sequence orthe like. It will be understood that when an element is referred to asbeing “on”, “connected to” or “coupled to” another element, it can bedirectly on, connected or coupled to the other element or interveningelements may be present. In contrast, when an element is referred to asbeing “directly on,” “directly connected to” or “directly coupled to”another element, there are no intervening elements present.

In the described exemplary system, although methods are described basedon a flowchart as a series of steps or blocks, aspects of the presentinvention are not limited to the sequence of the steps and a step may beexecuted in a different order or may be executed in parallel withanother step. In addition, it is apparent to those skilled in the artthat the steps in the flowchart are not exclusive, and another step maybe included or one or more steps of the flowchart may be omitted withoutaffecting the scope of the present invention. When an embodiment isembodied as software, the described scheme may be embodied as a module(process, function, or the like) that executes the described function.The module may be stored in a memory and may be executed by a processor.The memory may be disposed inside or outside the processor and may beconnected to the processor through various well-known means.

Further, the description described herein is related to a wirelesscommunication network, and an operation performed in a wirelesscommunication network may be performed in a process of controlling anetwork and transmitting data by a system that controls a wirelessnetwork, e.g., a base station, or may be performed in a user equipmentconnected to the wireless communication network.

It is apparent that a base station or other network nodes other than thebase station may be capable of performing various operations performedfor communication with a terminal in a network including a plurality ofnetwork nodes including the base station. The ‘BS (Base Station)’ may bereplaced with the terms, such as, a fixed station, a Node B, an eNode B(eNB), a gNodeB (gNB), an AP (Access Point), and the like. Also, the‘terminal’ may be replaced with the terms, such as a UE (UserEquipment), an MS (Mobile Station), an MSS (Mobile Subscriber Station),an SS (Subscriber Station), a non-AP STA (non-AP station), and the like.

In the present disclosure, transmitting or receiving a channel mayinclude the meaning of transmitting or receiving a signal or informationthrough the corresponding channel. For example, transmitting a controlchannel may indicate that a control signal or control information istransmitted through the control channel. Similarly, transmitting a datachannel may indicate that transmitting a data signal or data informationis transmitted through the data channel.

Hereinafter, the term “NR system” is used to distinguish a system towhich various embodiments of the present disclosure are applied from theconventional system. However, the scope of the present disclosure maynot be limited by the term. Also, the term “NR system” in the presentspecification is used as an example of a wireless communication systemthat is capable of supporting various numerologies. However, the term“NR system” is not limited to a wireless communication system thatsupports a plurality of SCSs.

First, a numerology that is considered by the NR system will bedescribed.

An NR numerology may indicate the numerical value of the basic elementor factor that generates a resource grid in the time-frequency domainfor designing the NR system. For example, as an example of thenumerology of the 3GPP LTE/LTE-A system, subcarrier spacing correspondsto 15 kHz (or 7.5 kHz in the case of MBSFN (Multicast-BroadcastSingle-Frequency Network)). In this instance, the term “numerology” isnot limited to subcarrier spacing, and may include the length of CP(Cyclic Prefix), the length of a TTI (Transmit Time Interval), thenumber of OFDM (Orthogonal Frequency Division Multiplexing) symbolswithin a predetermined time interval, the duration of a single OFDMsymbol, or the like, which is associated with subcarrier spacing (orwhich is determined based on subcarrier spacing). That is, differentnumerologies may be distinguished by a difference in at least one ofsubcarrier spacing, a CP length, a TTI length, the number of OFDMsymbols within a predetermined time interval, or the duration of asingle OFDM symbol.

In order to satisfy the requirements from “IMT for 2020 and beyond”, thecurrent 3GPP NR system considers a plurality of numerologies by takinginto consideration various scenarios, various service requirements,compatibility with a potential new system, or the like. Moreparticularly, the numerology of the conventional wireless communicationsystem is difficult to support a high frequency band, a fast movingspeed, a low latency, or the like which required from “IMT for 2020 andbeyond”, and thus, it is needed to define a new numerology.

For example, the NR system is capable of supporting applications, suchas eMBB(enhanced Mobile Broadband), mMTC(massive Machine TypeCommunications)/uMTC(Ultra Machine Type Communications), URLLC(Ultra-Reliable and Low Latency Communications), and the like.Particularly, the requirement associated with a user plane latency forURLLC and eMBB services is 0.5 ms in an uplink and is 4 ms in bothuplink and downlink, which requires a significant decrease in thelatency when compared to 10 ms, which is the requirement associated withthe latency of 3GPP LTE (Long Term Evolution) and LTE-A (LTE-Advanced)system.

To enable a single NR system to satisfy various scenarios and variousrequirements, the NR system needs to support various numerologies.Particularly, the NR system needs to support a plurality of SCSs, unlikethe conventional LTE/LTE-A system that supports a single subcarrierspacing (SCS) basically.

A new numerology for the NR system including supporting of a pluralityof SCSs may be determined by assuming a wireless communication systemthat operates in a frequency range or carrier, such as 6 GHz or 40 GHz,in order to overcome the problems in that a broadband cannot be used inthe conventional frequency range or carrier, such as 700 MHz or 2 GHz.However, the scope of the present disclosure may not be limited thereto.

In the NR system as described above, a Demodulation Reference Signal(DMRS) for demodulating a predetermined physical channel is required.For example, a DMRS for demodulating a physical data channel, a DMRS fordemodulating a physical control channel, or the like may be defined inthe NR system.

Particularly, the NR system may support a maximum of 8 layers or amaximum of 16 layers for a Single User (SU)-MIMO and may support amaximum of 12 orthogonal layers for Multiple User (MU)-MIMOtransmission. Such layers may be mapped onto antenna ports (i.e.,logical antennas), and may be transmitted via a physical channel. Inorder to correctly demodulate a signal transmitted via each layer orantenna port of the physical channel, a reference signal for thecorresponding layer or the corresponding antenna port is needed, whichis referred to as a DMRS.

The present disclosure will describe examples associated withdetermining DMRS mapping time-frequency resource, determining a new DMRSconfiguration for multiplexing a DMRS for different antenna ports mappedonto the same time-frequency resource, and signaling the DMRSconfiguration to each terminal by a base station, in order to support anincreased number of layers and an increased number of antenna ports inthe NR system.

Hereinafter, various examples associated with a DMRS layer, an antennaport, a sequence, and multiplexing for the NR system will be described.The examples are associated with new DMRS configuration which is capableof supporting the requirements of both SU-MIMO and MU-MIMO in the NRsystem. Also, the examples may correspond to the method of configuring aDMRS by taking into consideration basic DL transmission from a basestation to a terminal in the NR system, or may correspond to the methodof configuring a DMRS for MU-MIMO, which takes into consideration bothSL and DL (i.e., configuration for an SL DMRS and configuration for a DLDMRS). The present disclosure is not limited thereto, and may includeexamples of DMRS configuration for various purposes, which can besupported by the NR system.

In the following examples, it is assumed that a maximum of 12 DMRSorthogonal antenna ports (hereinafter, DMRS antenna ports) are used. Forexample, DMRS antenna port numbers #1, #2, #3, #4, #5, #6, #7, #8, #9,#10, #11, and #12 are defined. However, a different number may beactually given as a DMRS antenna port number in order to distinguish theDMRS antenna port number from a different type of RS antenna portnumber. When #p is given as a first DMRS antenna port number, #p, #p+1,#p+2, #p+3, #p+4, #p+5, #p+6, #p+7, #p+8, #p+9, #p+10, and #p+11 may begiven as the 12 DMRS antenna port numbers.

Also, it is assumed that the maximum number of DMRS layers that may beallocated to each terminal is 16 or 8.

When the number of DMRS layers that may be allocated to each terminal is16, each layer may correspond to a combination of an antenna port and atype of sequence. The sequence type may be identified based on ascrambling ID (SCID) used for generating a sequence that is used as aDMRS. For example, a DMRS sequence generated using A as an SCID valuemay be distinguished from a DMRS sequence generated using B as an SCIDvalue. For example, the antenna port-SCID combination for a DMRS may bedefined as list in Table 1, each of the 16 layers may correspond to oneof the combinations.

TABLE 1 combination antenna port scrambling ID #1 #1 A #2 #2 A #3 #3 A#4 #4 A #5 #5 A #6 #6 A #7 #7 A #8 #8 A #9 #9 A #10 #10 A #11 #11 A #12#12 A #13 #9 B #14 #10 B #15 #11 B #16 #12 B

In Table 1, DMRS antenna port numbers #1 to #8 may use a sequencegenerated based on one SCID (e.g., A), and DMRS antenna port numbers #9to #12 may use sequences generated based on two SCIDs (e.g., A and B).

Also, as the SCID value, A=0 and B=1. However, the SCID value is notlimited thereto. For example, when a DMRS is based on a Pseudo-randomNoise (PN) sequence, the initial value of the PN sequence may includethe SCID. Alternatively, the initial value of the PN sequence mayinclude a value specific to one of a cell (or a terminal group), a time,and a frequency, but the initial value is not limited thereto.

When the number of DMRS layers that may be allocated to each terminal is8, each layer may correspond to one of the eight DMRS antenna portsselected from among the DMRS antenna ports #1, #2, #3, #4, #5, #6, #7,#8, #9, #10, #11, and #12.

Hereinafter, examples of a DMRS pattern for the NR system will bedescribed.

The DMRS pattern may include a time-frequency resource to which a DMRSis mapped, and a method of multiplexing different DMRS antenna portsthat are mapped onto the same time-frequency resource.

In the NR system, a DMRS mapping resource may be defined based on aPhysical Resource Block (PRB) unit, which is defined by one slot in thetime-domain and 12 subcarriers in the frequency-domain. Here, one slotindicates a time unit corresponding to a total of seven symbols and atotal of 14 symbols according to SCS in the time-domain. Also, aphysical resource unit corresponding to one symbol and one subcarrier isa Resource Element (RE). Therefore, one PRB may include 7*12 REs or14*12 REs according to SCS.

A DMRS for the NR system may be disposed in one or two consecutive OFDMsymbols in the front part of one slot from the perspective of time, andan additional DMRS (e.g., a DMRS used when a channel that dramaticallychanges over time due to fast movement speed needs to be supported) maybe disposed in the rear part of the slot.

The additional DMRS may be applied to a high Doppler scenario, and mayhave the same or lower density on the frequency domain than that of theDMRS disposed in the front part of the slot.

Also, at least, in the case of Cyclic Prefix (CP)-OFDM, a DMRS structurethat is common to DL and UL may be supported in the NR system. Forexample, DMRSs for the same link or DMRSs for different links may beconfigured to be orthogonal to each other.

For DL DMRS antenna port multiplexing, at least one of FrequencyDivision Multiplexing (FDM), Time Division Multiplexing (TDM), and CodeDivision Multiplexing (CDM) may be applied. As multiplexing resourcesfor CDM, code resources, such as a Orthogonal Cover Code (OCC), CyclicShift (CS), or the like may be used. Also, CDM may be applied in thetime-domain, the frequency-domain, or the time-frequency domain.

FIG. 1 is a diagram illustrating examples of a DMRS pattern according tothe present disclosure.

FIG. 1 illustrates the case in which 12 DMRS antenna ports areconfigured as six Code Division Multiplexing (CDM) groups. For example,two DMRS antenna ports may be included in one CDM group, as listed inTable 2 provided below.

TABLE 2 CDM group antenna port #A #1, #2 #B #3, #4 #C #5, #6 #D #7, #8#E  #9, #10 #F #11, #12

In Table 2, different CDM groups may be separated by one or more ofdifferent frequency resources and different time resources. Here, thefrequency resources may be subcarriers, and the time resources may besymbols. That is, DMRS antenna ports included in different CDM groupsmay be mapped onto different subcarriers, thereby being multiplexedaccording to Frequency Division Multiplexing (FDM) scheme, may be mappedonto different OFDM symbols, thereby being multiplexed according to TimeDivision Multiplexing (TDM) scheme, or may be mapped onto differentsubcarriers and different OFDM symbols, thereby being multiplexedaccording to the FDM and TDM schemes.

Two DMRS antenna ports included in the same CDM group may bedistinguished by an Orthogonal Cover Code (OCC). An OCC having a lengthof 2 may be used to distinguish two antenna ports. Also, the OCC may beapplied in the time-domain, or to the frequency-domain. For example, thelength-2 OCC may be applied to two OFDM symbols, or two subcarriers.

FIG. 1 illustrates REs onto which a DMRS is mapped in one PRB. Thesymbol index 1 may correspond to the index of a first symbol remainingafter excluding a control region from one slot (e.g., 1=2). Also, 12subcarriers in the frequency-domain may be subcarriers belonging to anm^(th) PRB.

In FIG. 1, (a) illustrates the case in which a DMRS is mapped onto amaximum of 3 symbols (i.e., 1, 1+1, and 1+1′) in one slot. Here, 1′ maybe a value greater than 2.

Also, (a) of the FIG. 1 illustrates an example in which a length-2 OCCis applied in the frequency-domain. Particularly, CDM groups #A and #Bmay be mapped onto the symbol index 1, and they are distinguishedaccording to the FDM scheme. CDM groups #C and #D may be mapped onto thesymbol index 1+1, and they are distinguished according to the FDMscheme. CDM groups #E and #F may be mapped onto the symbol index 1+1′,and they are distinguished according to the FDM scheme.

Each CDM group may be repeated a maximum of three times within one PRBin the frequency-axis. That is, the maximum overhead occupied by oneport in one PRB may be three REs.

(b) of the FIG. 1 illustrates the case in which a DMRS is mapped onto amaximum of 2 symbols (i.e., 1 and 1+1) in one slot.

Also, (b) of the FIG. 1 illustrates an example in which a length-2 OCCis applied in the frequency-domain. Particularly, CDM groups #A, #B, and#C may be mapped onto the symbol index 1, and they are distinguishedaccording to the FDM scheme. CDM groups #D, #E, and #F may be mappedonto the symbol index 1+1′, and they are distinguished according to theFDM scheme.

Each CDM group may be repeated a maximum of two times within one PRB inthe frequency-axis. That is, the maximum overhead occupied by one portin one PRB may be two REs.

(c) of the FIG. 1 illustrates the case in which a DMRS is mapped onto amaximum of 4 symbols (i.e., 1, 1+1, 1+1′, and 1+1′+1) in one slot.

Also, (c) in FIG. 1 illustrates an example in which a length-2 OCC isapplied in the time-domain. Particularly, CDM groups #A, #B, #C, and #Dmay be mapped onto the symbol indices 1 and 1+1, and they aredistinguished according to the FDM scheme. CDM groups #E and #F may bemapped onto the symbol indices 1+1′ and 1+1′+1, and they aredistinguished according to the FDM scheme.

Each CDM group may be repeated a maximum of three times within one PRBin the frequency-axis. That is, the maximum overhead occupied by oneport in one PRB may be three REs.

(d) of the FIG. 1 illustrates the case in which a DMRS is mapped onto amaximum of 2 symbols (i.e., 1 and 1+1) in one slot.

Also, (d) of the FIG. 1 illustrates an example in which a length-2 OCCis applied in the time-domain. Particularly, CDM groups #A, #B, #C, #D,#E, and #F may be mapped onto the symbol indices 1 and 1+1, and they aredistinguished according to the FDM scheme.

Each CDM group may be repeated a maximum of two times within one PRB inthe frequency-axis. That is, the maximum overhead occupied by one portin one PRB may be two REs.

FIG. 2 is a diagram illustrating additional examples of a DMRS patternaccording to the present disclosure.

FIG. 2 illustrates the case in which 12 DMRS antenna ports areconfigured as three CDM groups (e.g., each of the 12 DMRS antenna portsis classified into one of the three CDM groups). For example, four DMRSantenna ports may be included in one CDM group, as listed in Table 3provided below.

TABLE 3 CDM group antenna port #A #1, #2, #3, #4 #B #5, #6, #7, #8 #C#9, #10, #11, #12

In Table 3, different CDM groups may be separated by one or more ofdifferent frequency resources and/or different time resources. Here, thefrequency resources may be subcarriers, and the time resources may besymbols. That is, DMRS antenna ports included in different CDM groupsmay be mapped onto different subcarriers, thereby being multiplexedaccording to the FDM scheme, may be mapped onto different OFDM symbols,thereby being multiplexed according to the TDM scheme, or may be mappedonto different subcarriers and different OFDM symbols, thereby beingmultiplexed according to the FDM and TDM schemes.

Four DMRS antenna ports included in the same CDM group may bedistinguished by an OCC. An OCC having a length of 4 may be used todistinguish four antenna ports. Also, the OCC may be applied in thetime-domain, the frequency-domain, or the time-frequency domains. Forexample, the length-4 OCC may be applied to i) four OFDM symbols, ii)four subcarriers, or iii) two OFDM symbols and two subcarriers.

FIG. 2 illustrates REs onto which a DMRS is mapped in one PRB. Thesymbol index 1 may correspond to the index of a first symbol remainingafter excluding a control region from one slot (e.g., 1=2). Also, 12subcarriers in the frequency-domain may be subcarriers belonging to anm^(th) PRB.

In FIG. 2, (a) illustrates the case in which a DMRS is mapped onto amaximum of 3 symbols (i.e., 1, 1+1, and 1+1′) in one slot. Here, 1′ maybe a value greater than 2.

Also, (a) of the FIG. 2 illustrates an example in which a length-4 OCCis applied in the frequency-domain. Particularly, CDM group #A may bemapped onto the symbol index 1, and CDM group #B may be mapped onto thesymbol index 1+1, and the CDM group #C may be mapped onto the symbolindex 1+1′.

Each CDM group may be repeated a maximum of times within one PRB in thefrequency-axis. That is, the maximum overhead occupied by one port inone PRB may be three REs.

(b) of the FIG. 2 illustrates the case in which a DMRS is mapped onto amaximum of 2 symbols (i.e., 1 and 1+1) in one slot.

Also, (b) of the FIG. 2 illustrates an example in which a length-4 OCCis applied in the frequency-domain.

For example, CDM groups #A, #B, and #C may be mapped onto the symbolindex 1, and they are distinguished according to the FDM scheme. Forexample, CDM groups #A, #B, and #C may be mapped onto the symbol index1+1, and they are distinguished according to the FDM scheme. Here,corresponding CDM groups may be configured in only one symbol or in bothtwo symbols according to overhead.

That is, each of the CDM group #A, the CDM group #B, and the CDM group#C may be configured in the symbol index 1, and may be additionallyconfigured in the symbol index 1+1 according to overhead. Alternatively,the CDM group #A may be configured in only the symbol index 1 once orrepeatedly two times according to overhead. The CDM group #B may beconfigured in only the symbol index 1+1 once or repeatedly two timesaccording to overhead. The CDM group #C may be configured in only thesymbol index 1 or may be configured in both the symbol index 1 andsymbol index 1+1, according to overhead.

Each CDM group may be repeated a maximum of two times within one PRB inthe frequency-axis. That is, the maximum overhead occupied by one portin one PRB may be two REs.

(c) of the FIG. 2 illustrates the case in which a DMRS is mapped onto amaximum of 4 symbols (i.e., 1, 1+1, 1+1′, and 1+1′+1) in one slot.

Also, (c) of the FIG. 2 illustrates an example in which a length-4 OCCis applied in the frequency-domain. Particularly, CDM groups #A and #Bmay be mapped onto the symbol indices 1 and 1+1, and they aredistinguished according to the FDM scheme. The CDM group #C may bemapped onto the symbol indices 1+1′ and 1+1′+1.

Each CDM group may be repeated a maximum of three times within one PRBin the frequency-axis. That is, the maximum overhead occupied by oneport in one PRB may be three REs.

(d) of the FIG. 2 illustrates the case in which a DMRS is mapped onto amaximum of 2 symbols (i.e., 1 and 1+1) in one slot.

Also, (d) of the FIG. 2 illustrates an example in which a length-4 OCCis applied in the frequency-domain. Particularly, CDM groups #A, #B, and#C may be mapped onto the symbol indices 1 and 1+1, and they aredistinguished according to the FDM scheme.

Each CDM group may be repeated a maximum of two times within one PRB inthe frequency-axis. That is, the maximum overhead occupied by one portin one PRB may be two REs.

Hereinafter, examples of a DMRS pattern according to the presentdisclosure will be described in detail. The examples of a DMRS patterndescribed in the following description may correspond to a DMRS patternin one PRB (e,g., an m^(th) PRB) corresponding to one slot (an n^(th)slot) in the time-domain and 12 subcarriers in the frequency domain. TheDMRS pattern may be repeated in one or more additional slots or one ormore PRBs.

In the examples of FIGS. 3 to 6 described below, two DMRS antenna portsmay be mapped onto one CDM group, and a total of 6 CDM groups may beconfigured for a total of 12 DMRS antenna ports, as shown in FIG. 1 andTable 2.

FIG. 3 is a diagram illustrating an example of a DMRS pattern in one PRBaccording to the present disclosure.

The examples of FIG. 3 may correspond to detailed examples similar tothe DMRS pattern of (a) of the FIG. 1. That is, basically, in the DMRSpattern of FIG. 3, CDM groups #A and #B, which are distinguishedaccording to the FDM scheme, may be mapped onto a first symbol. CDMgroups #C and #D, which are distinguished according to the FDM scheme,may be mapped onto a second symbol. CDM groups #E and #F, which aredistinguished according to the FDM scheme, may be mapped onto a thirdsymbol.

The OCC mapping scheme will be described with reference to (a) of theFIG. 3.

As illustrated in (a) of FIG. 3, in all cases, with respect to two REsin the frequency axis within one symbol to which corresponding CDMgroups are mapped, a is applied to a first RE (e.g., an RE having a lowsubcarrier index) as an OCC value. b is applied to a second RE (e.g., anRE having a high subcarrier index) as an OCC value. The OCC values, aand b, may be given as listed in Table 4 provided below.

TABLE 4 1st antenna port 2nd antenna port OCC value in each CDM group ineach CDM group a +1 +1 b +1 −1

For example, for the DMRS antenna port #1 of the CDM group #A, OCCs of+1 and +1 may be applied to two REs in the frequency axis. For the DMRSantenna port #2 of the CDM group #A, OCCs of +1 and −1 may be applied totwo REs in the frequency axis.

Each CDM group may be repeated once for the (b), two times of the (c),or three times of the (d) of the in the FIG. 3 within a PRB in thefrequency axis.

As illustrated in (b) of the FIG. 3, when a DMRS mapping pattern isrepeated once within one PRB, DMRS overhead may be expressed as 1 RE per1 port and 1 PRB. That is, one CDM group is mapped onto a total of twoREs in one PRB, and two DMRS antenna ports are included in one CDM groupand thus, it is expressed that one DMRS antenna port has overheadcorresponding to one RE.

(b) of the FIG. 3 illustrates an example in which each CDM group appliesa lengh-2 OCC-based CDM (i.e., CDM2) in the frequency axis to twocontiguous or discontiguous REs in the frequency axis within one symbol,and repeats this once within one PRB in the frequency axis (i.e., twoREs are used for two DMRS antenna ports within one PRB). A specificsymbol index in a slot and a subcarrier position in the PRB for DMRS REsof (b) of the FIG. 3 are not limited, and may be determined according toa previously fixed position or a position obtained from signaling by abase station.

As illustrated in (c) of the FIG. 3, when a DMRS mapping pattern isrepeated two times within one PRB, DMRS overhead may be expressed as 2REs per 1 port and 1 PRB. That is, one CDM group is mapped onto a totalof four REs in one PRB, and two DMRS antenna ports are included in oneCDM group and thus, it is expressed that one DMRS antenna port hasoverhead corresponding to two REs.

The (c) of the FIG. 3 illustrates an example in which each CDM groupapplies a lengh-2 OCC-based CDM (i.e., CDM2) in the frequency-axis totwo contiguous or discontiguous REs in the frequency axis within onesymbol, and repeats this two times within one PRB in the frequency axis(i.e., four REs are used for two DMRS antenna ports within one PRB). Aspecific symbol index in a slot and a subcarrier position in a PRB forDMRS REs of (c) of the FIG. 3 are not limited, and may be determinedaccording to a previously fixed position or a position obtained fromsignaling by a base station.

As illustrated in (d) of the FIG. 3, when a DMRS mapping pattern isrepeated three times within one PRB, DMRS overhead may be expressed as 3REs per 1 port and 1 PRB. That is, one CDM group is mapped onto a totalof six REs in one PRB, and two DMRS antenna ports are included in oneCDM group and thus, it is expressed that one DMRS antenna port hasoverhead corresponding to three REs.

The (d) of the FIG. 3 illustrates an example in which each CDM groupapplies a lengh-2 OCC-based CDM (i.e., CDM2) in the frequency axis totwo contiguous or discontiguous REs in the frequency axis within onesymbol, and repeats this three times within one PRB in the frequencyaxis (i.e., six REs are used for two DMRS antenna ports within one PRB).A specific symbol index in a slot and a subcarrier position in a PRB forDMRS REs of (d) of the FIG. 3 are not limited, and may be determinedaccording to a previously fixed position or a position obtained fromsignaling by a base station.

An additional DMRS may be mapped onto the rear part of the slot bytaking into consideration a high Doppler scenario, using the basicpatterns of the (b) to (d) in FIG. 3.

Particularly, the patterns onto which a DMRS is mapped in the (b) to (d)in FIG. 3 (patterns indicating relative positions of REs onto which aDMRS is mapped in the time-frequency domain, excluding a specific symbolindex and a specific subcarrier index as illustrated in (a) in theFIG. 1) may be defined as patterns 1-1, 1-2, and 1-3, respectively.Based on the above, a DMRS according to a basic pattern may be mappedonto the front part in one slot from the perspective of time, and a DMRSaccording to an additional pattern may be mapped onto the rear part inthe same slot, as shown in Table 5 provided below.

TABLE 5 DMRS pattern Basic pattern Additional pattern embodiments (frontpart of slot) (rear part of slot) 1 1-1 None 2 1-2 None 3 1-3 None 4 1-11-1 5 1-1 1-2 6 1-1 1-3 7 1-2 1-1 8 1-2 1-2 9 1-2 1-3 10 1-3 1-1 11 1-31-2 12 1-3 1-3

The examples of (e) and (f) in the FIG. 3 may correspond to DMRS patternembodiments 10 and 12 of Table 5.

FIG. 4 is a diagram illustrating an additional example of a DMRS patternin one PRB according to the present disclosure.

The examples of FIG. 4 may correspond to detailed examples similar tothe DMRS pattern of (b) of the FIG. 1. That is, basically, in the DMRSpattern of FIG. 4, CDM groups #A, #B, and #C, which are distinguishedaccording to the FDM scheme, may be mapped onto a first symbol. CDMgroups #D, #E, and #F, which are distinguished according to the FDMscheme, may be mapped onto a second symbol.

The OCC mapping scheme will be described with reference to (a) of theFIG. 4.

As illustrated in (a) of the FIG. 4, in all cases, with respect to twoREs in the frequency axis within one symbol to which corresponding CDMgroups are mapped, A is applied to a first RE (e.g., an RE having a lowsubcarrier index) as an OCC value. B is applied to a second RE (e.g., anRE having a high subcarrier index) as an OCC value. The OCC values a andb may be given as listed in Table 6 provided below.

TABLE 6 1st antenna port 2nd antenna port OCC value in each CDM group ineach CDM group A +1 +1 B +1 −1

For example, for the DMRS antenna port #1 of the CDM group #A, OCCs of+1 and +1 may be applied to two REs in the frequency direction. For theDMRS antenna port #2 of the CDM group #A, OCCs of +1 and −1 may beapplied to two REs in the frequency axis.

Each CDM group may be repeated once of the (b) or two times of the (c)in FIG. 4 within one PRB in the frequency axis.

As illustrated in (b) in the FIG. 4, when a DMRS mapping pattern isrepeated once within one PRB, DMRS overhead may be expressed as 1 RE per1 port and 1 PRB. That is, one CDM group is mapped onto two REs in onePRB, and two DMRS antenna ports are included in one CDM group and thus,it is expressed that one DMRS antenna port has overhead corresponding toone RE.

(b) in the FIG. 4 illustrates an example in which each CDM group appliesa lengh-2 OCC-based CDM (i.e., CDM2) in the frequency axis to twocontiguous or discontinuous REs in the frequency axis within one symbol,and repeats this once within one PRB in the frequency axis (i.e., twoREs are used for two DMRS antenna ports within one PRB). A specificsymbol index in a slot and a subcarrier position in a PRB for DMRS REsof (b) in the FIG. 4 are not limited, and may be determined according toa previously fixed position or a position obtained from signaling by abase station.

As illustrated in (c) of the FIG. 4, when a DMRS mapping pattern isrepeated two times within one PRB, DMRS overhead may be expressed as 2REs per 1 port and 1 PRB. That is, one CDM group is mapped onto a totalof four REs in one PRB, and two DMRS antenna ports are included in oneCDM group and thus, it is expressed that one DMRS antenna port hasoverhead corresponding to two REs.

The (c) of the FIG. 4 illustrates an example in which each CDM groupapplies a lengh-2 OCC-based CDM (i.e., CDM2) in the frequency axis totwo contiguous or discontiguous REs in the frequency axis within onesymbol, and repeats this two times within one PRB in the frequency axis(i.e., four REs are used for two DMRS antenna ports within one PRB). Aspecific symbol index in a slot and a subcarrier position in a PRB forDMRS REs of the (c) of the FIG. 4 are not limited, and may be determinedaccording to a previously fixed position or a position obtained fromsignaling by a base station.

An additional DMRS may be mapped onto the rear part of the slot bytaking into consideration a high Doppler scenario, using the basicpatterns of the (b) and (c) in the FIG. 4.

Particularly, the patterns onto which a DMRS is mapped in FIGS. 4B and4C (patterns indicating relative positions of REs onto which a DMRS ismapped in the time-frequency domain, excluding a specific symbol indexand a specific subcarrier index as illustrated in the (b) in the FIG. 1may be defined as patterns 2-1 and 2-2, respectively. Based on theabove, a DMRS according to a basic pattern may be mapped onto the frontpart in one slot from the perspective of time, and a DMRS according toan additional pattern may be mapped onto the rear part in the same slot,as shown in Table 7 provided below.

TABLE 7 DMRS pattern Basic pattern Additional pattern embodiments (frontpart of slot) (rear part of slot) 13 2-1 None 14 2-2 None 15 2-1 2-1 162-1 2-2 17 2-2 2-1 18 2-2 2-2

The examples of (d) and (e) in the FIG. 4 may correspond to DMRS patternembodiments 17 and 18 of Table 7, respectively.

As an additional example, based on patterns 2-1 and 2-2, a DMRSaccording to the basic pattern is mapped onto the front part of one slotfrom the perspective of time, and DMRSs according to a first additionalpattern and a second additional pattern may be mapped onto the rear partof one slot, as list in Table 8 provided below.

TABLE 8 Basic pattern Second additional DMRS pattern (front part Firstadditional pattern pattern embodiments of slot) (rear part of slot)(rear part of slot) 19 2-1 None None 20 2-2 None None 21 2-1 2-1 None 222-1 2-2 None 23 2-2 2-1 None 24 2-2 2-2 None 25 2-1 2-1 2-1 26 2-1 2-12-2 27 2-1 2-2 2-1 28 2-1 2-2 2-2 29 2-2 2-1 2-1 30 2-2 2-1 2-2 31 2-22-2 2-1 32 2-2 2-2 2-2

The examples of (f) and (g) of the FIG. 4 may correspond to DMRS patternembodiments 29 and 32 of Table 8, respectively.

FIG. 5 is a diagram illustrating an additional example of a DMRS patternin one PRB according to the present disclosure.

The examples of FIG. 5 may correspond to detailed examples similar tothe DMRS pattern of (c) in the FIG. 1. That is, basically, in the DMRSpattern of FIG. 5, CDM groups #A, #B, #C, and #D, which aredistinguished according to the FDM scheme, may be mapped onto a firstsymbol and a second symbol. CDM groups #E and #F, which aredistinguished according to the FDM scheme, may be mapped onto a thirdsymbol and a fourth symbol. The OCC mapping scheme will be describedwith reference to (a) in the FIG. 5.

As illustrated in (a) in the FIG. 5, mapping scheme case #1 and mappingscheme case #2 may be alternately applied in the frequency axis withrespect to two REs, which are in the same position or differentpositions in the frequency axis in two symbols to which correspondingCDM groups are mapped. According to the mapping scheme case #1, a may beapplied to a first RE (e.g., an RE having a low symbol index) as an OCCvalue. b may be applied to a second RE (e.g., an RE having a high symbolindex) as an OCC value. According to the mapping scheme case #2, b maybe applied to a first RE (e.g., an RE having a low symbol index) as anOCC value, and a may be applied to a second RE (e.g., an RE having ahigh symbol index) as an OCC value. When the same OCC value (e.g., a) ismapped onto one symbol, power balancing problem may occur. Accordingly,as described above, the case#1 and the case #2 are alternately appliedin the frequency domain, so as to alternately map different OCC values aand b, onto one symbol. For example, in the case in which a CDM group isrepeated C times in the frequency axis with respect to two symbols towhich corresponding CDM groups are mapped, when the repetition indicesare 0, 1, . . . , and C−1, the case #1 may be applied to an indexcorresponding to even-numbered repetition, and the case #2 may beapplied to an index corresponding to an odd-numbered repetition.

The OCC values a and b may be given as listed in Table 9 provided below.

TABLE 9 1st antenna port 2nd antenna port OCC value in each CDM group ineach CDM group a +1 +1 b +1 −1

For example, for the DMRS antenna port #1 of the CDM group #A, OCCs of+1 and +1 may be applied to two REs in the time axis. For the DMRSantenna port #2 of the CDM group #A, OCCs of +1 and −1 may be applied totwo REs in the time axis.

Each CDM group may be repeated once of the (b), two times of the (c), orthree times of the (d) of the FIG. 5 within one PRB in the frequencyaxis.

As illustrated in (b) in the FIG. 5, when a DMRS mapping pattern isrepeated once within one PRB, DMRS overhead may be expressed as 1 RE per1 port and 1 PRB. That is, one CDM group is mapped onto two REs in onePRB, and two DMRS antenna ports are included in one CDM group and thus,it is expressed that one DMRS antenna port has overhead corresponding toone RE.

The (b) in the FIG. 5 illustrates an example in which each CDM groupapplies a lengh-2 OCC-based CDM (i.e., CDM2) in the time axis withrespect to two REs, which are in the same position or differentpositions in the frequency axis in two contiguous or discontiguoussymbols, and repeats this once within one PRB (i.e., two REs are usedfor two DMRS antenna ports within one PRB). A specific symbol index in aslot and a subcarrier position in a PRB for DMRS REs of the (b) of theFIG. 5 are not limited, and may be determined according to a previouslyfixed position or a position obtained from signaling by a base station.

As illustrated in (c) of the FIG. 5, when a DMRS mapping pattern isrepeated two times within one PRB, DMRS overhead may be expressed as 2REs per 1 port and 1 PRB. That is, one CDM group is mapped onto a totalof four REs in one PRB, and two DMRS antenna ports are included in oneCDM group and thus, it is expressed that one DMRS antenna port hasoverhead corresponding to two REs.

The (c) in the FIG. 5 illustrates an example in which each CDM groupapplies a lengh-2 OCC-based CDM (i.e., CDM2) in the time axis withrespect to two REs, which are in the same position or differentpositions in the frequency axis in two contiguous or discontiguoussymbols, and repeats this two times within one PRB (i.e., four REs areused for two DMRS antenna ports within one PRB). A specific symbol indexin a slot and a subcarrier position in one PRB for DMRS REs of the (c)in the FIG. 5 are not limited, and may be determined according to apreviously fixed position or a position obtained from signaling by abase station.

As illustrated in (d) in the FIG. 5, when a DMRS mapping pattern isrepeated three times within one PRB, DMRS overhead may be expressed as 3REs per 1 port and 1 PRB. That is, one CDM group is mapped onto a totalof six REs in one PRB, and two DMRS antenna ports are included in oneCDM group and thus, it is expressed that one DMRS antenna port hasoverhead corresponding to three REs.

The (d) in the FIG. 5 illustrates an example in which each CDM groupapplies a lengh-2 OCC-based CDM (i.e., CDM2) to two REs in the timeaxis, which are in the same position or different positions in thefrequency axis in two contiguous or discontiguous symbols, and repeatsthis three times within one PRB in the frequency axis (i.e., six REs areused for two DMRS antenna ports within one PRB). A specific symbol indexin a slot and a subcarrier position in a PRB for DMRS REs of (b) in theFIG. 5 are not limited, and may be determined according to a previouslyfixed position or a position obtained from signaling by a base station.

An additional DMRS may be mapped onto the rear part of the slot bytaking into consideration a high Doppler scenario, using the basicpatterns of (b) to (d) in the FIG. 5.

Particularly, the patterns onto which a DMRS is mapped in the (b) to (d)in the FIG. 5 (patterns indicating relative positions of REs onto whicha DMRS is mapped in the time-frequency domain, excluding a specificsymbol index and a specific subcarrier index as illustrated in (c) ofthe FIG. 1) may be defined as patterns 3-1, 3-2, and 3-3, respectively.Based on the above, a DMRS according to a basic pattern may be mappedonto the front part in one slot from the perspective of time, and a DMRSaccording to an additional pattern may be mapped onto the rear part inthe same slot, as shown in Table 10 provided below.

TABLE 10 DMRS pattern Basic pattern Additional pattern embodiments(front part of slot) (rear part of slot) 33 3-1 None 34 3-2 None 35 3-3None 36 3-1 3-1 37 3-1 3-2 38 3-1 3-3 39 3-2 3-1 40 3-2 3-2 41 3-2 3-342 3-3 3-1 43 3-3 3-2 44 3-3 3-3

The examples of (e) and (f) in the FIG. 5 may correspond to DMRS patternembodiments 42 and 44 of Table 10, respectively.

FIG. 6 is a diagram illustrating an additional example of a DMRS patternin one PRB according to the present disclosure.

The examples of FIG. 6 may correspond to detailed examples similar tothe DMRS pattern of (d) of FIG. 1. That is, basically, in the DMRSpattern of FIG. 6, CDM groups #A, #B, #C, #D, #E, and #F, which aredistinguished according to the FDM scheme, may be mapped onto a firstsymbol and a second symbol.

The OCC mapping scheme will be described with reference to (a) the FIG.6.

As illustrated in the (a) in the FIG. 6, mapping scheme case #1 andmapping scheme case #2 may be alternately applied in the frequency axiswith respect to two REs, which are in the same position or differentpositions in the frequency axis in two symbols to which correspondingCDM groups are mapped. According to the mapping scheme case #1, a may beapplied to a first RE (e.g., an RE having a low symbol index) as an OCCvalue. b may be applied to a second RE (e.g., an RE having a high symbolindex) as an OCC value. According to the mapping scheme case #2, b maybe applied to a first RE (e.g., an RE having a low symbol index) as anOCC value, and a may be applied to a second RE (e.g., an RE having ahigh symbol index) as an OCC value.

When the same OCC value (e.g., a) is mapped onto one symbol, powerbalancing problem may occur. Accordingly, as described above, the case#1and the case #2 are alternately applied in the frequency axis, so as toalternately map different OCC values a and b onto one symbol.

For example, in the case in which a CDM group is repeated C times in thefrequency axis with respect to two symbols to which corresponding CDMgroups are mapped, when the repetition indices are 0, 1, . . . , andC−1, the case #1 may be applied to an index corresponding toeven-numbered repetition, and the case #2 may be applied to an indexcorresponding to add-numbered repetition.

The OCC values a and b may be given as listed in Table 11 providedbelow.

TABLE 11 1st antenna port 2nd antenna port OCC value in each CDM groupin each CDM group a +1 +1 b +1 −1

For example, for the DMRS antenna port #1 of the CDM group #A, OCCs of+1 and +1 may be applied to two REs in the time axis. For the DMRSantenna port #2 of the CDM group #A, OCCs of +1 and −1 may be applied totwo REs in the time axis.

Each CDM group may be repeated once of the (b), or two times of the (c)in the FIG. 6 within one PRB in the frequency axis.

As illustrated in (b) in the FIG. 6, when a DMRS mapping pattern isrepeated once within one PRB, DMRS overhead may be expressed as 1 RE per1 port and 1 PRB. That is, one CDM group is mapped onto a total of twoREs in one PRB, and two DMRS antenna ports are included in one CDM groupand thus, it is expressed that one DMRS antenna port has overheadcorresponding to one RE.

The (b) in the FIG. 6 illustrates an example in which each CDM groupapplies a lengh-2 OCC-based CDM (i.e., CDM2) in the time axis withrespect to two REs, which are in the same position or differentpositions in the frequency axis in two continuous or discontiguoussymbols, and repeats this once within one PRB (i.e., two REs are usedfor two DMRS antenna ports within one PRB). A specific symbol index in aslot and a subcarrier position in a PRB for DMRS REs of the (b) in theFIG. 6 are not limited, and may be determined according to a previouslyfixed position or a position obtained from signaling by a base station.

As illustrated in (c) of the FIG. 6, when a DMRS mapping pattern isrepeated two times within one PRB, DMRS overhead may be expressed as 2REs per 1 port and 1 PRB. That is, one CDM group is mapped onto a totalof four REs in one PRB, and two DMRS antenna ports are included in oneCDM group and thus, it is expressed that one DMRS antenna port hasoverhead corresponding to two REs.

The (c) of the FIG. 6 illustrates an example in which each CDM groupapplies a lengh-2 OCC-based CDM (i.e., CDM2) in the time axis withrespect to two REs, which are in the same position or differentpositions in the frequency axis in two contiguous or discontiguoussymbols, and repeats this two times within one PRB (i.e., four REs areused for two DMRS antenna ports within one PRB). A specific symbol indexin a slot and a subcarrier position in a PRB for DMRS REs of (c) of theFIG. 6 are not limited, and may be determined according to a previouslyfixed position or a position obtained from signaling by a base station.

An additional DMRS may be mapped onto the rear part of the slot bytaking into consideration a high Doppler scenario, using the basicpatterns of (b) and (c) in the FIG. 6.

Particularly, the patterns onto which a DMRS is mapped in (b) and (c) inthe FIG. 6 (patterns indicating relative positions of REs onto which aDMRS is mapped in the time-frequency domain, excluding a specific symbolindex and a specific subcarrier index as illustrated in (a) in theFIG. 1) may be defined as patterns 4-1 and 4-2, respectively. Based onthe above, a DMRS according to the basic pattern may be mapped onto thefront part in one slot from the perspective of time, and a DMRSaccording to an additional pattern may be mapped onto the rear part inthe same slot, as shown in Table 12 provided below.

TABLE 12 DMRS pattern Basic pattern Additional pattern embodiments(front part of slot) (rear part of slot) 45 4-1 None 46 4-2 None 47 4-14-1 48 4-1 4-2 49 4-2 4-1 50 4-2 4-2

The examples of (d) and (e) in the FIG. 6 may correspond to DMRS patternembodiments 49 and 50 of Table 12, respectively.

As an additional example, based on patterns 4-1 and 4-2, a DMRSaccording to a basic pattern is mapped onto the front part of one slotfrom the perspective of time, and DMRSs according to a first additionalpattern and a second additional pattern may be mapped onto the rear partof one slot.

TABLE 13 Basic pattern Second additional DMRS pattern (front part Firstadditional pattern pattern embodiments of slot) (rear part of slot)(rear part of slot) 51 4-1 None None 52 4-2 None None 53 4-1 4-1 None 544-1 4-2 None 55 4-2 4-1 None 56 4-2 4-2 None 57 4-1 4-1 4-1 58 4-1 4-14-2 59 4-1 4-2 4-1 60 4-1 4-2 4-2 61 4-2 4-1 4-1 62 4-2 4-1 4-2 63 4-24-2 4-1 64 4-2 4-2 4-2

The examples of (f) and (g) in the FIG. 6 may correspond to DMRS patternembodiments 61 and 64 of Table 13, respectively.

In the examples of FIGS. 7 to 10 described below, four DMRS antennaports may be mapped onto one CDM group, and a total of 3 CDM groups maybe configured for a total of 12 DMRS antenna ports, as shown in FIG. 2and Table 3.

FIG. 7 is a diagram illustrating an additional example of a DMRS patternin one PRB according to the present disclosure.

The examples of FIG. 7 may correspond to detailed examples similar tothe DMRS pattern of (a) in the FIG. 2. That is, in the DMRS pattern ofFIG. 7, basically, CDM group #A may be mapped onto a first symbol, CDMgroup #B may be mapped onto a second symbol, and CDM group #C may bemapped onto a third symbol.

The OCC mapping scheme will be described with reference to (a) in theFIG. 7.

As illustrated in (a) in the FIG. 7, in all cases, with respect to fourREs in the frequency axis within one symbol to which corresponding CDMgroups are mapped, a is applied to a first RE (e.g., an RE having thelowest subcarrier index) as an OCC value. b is applied to a second RE(e.g., an RE having the second lowest subcarrier index) as an OCC value.c is applied to a third RE (e.g., an RE having the third lowestsubcarrier index) as an OCC value. d is applied to a fourth RE (e.g., anRE having the highest subcarrier index) as an OCC value.

The OCC values a, b, c, and d may be given as listed in Table 12provided below.

TABLE 14 1st antenna 2nd antenna 3rd antenna 4th antenna port port portport OCC in each CDM in each CDM in each CDM in each CDM value groupgroup group group a +1 +1 +1 +1 b +1 −1 +1 −1 c +1 +1 −1 −1 d +1 −1 −1+1

For example, for the DMRS antenna port #1 of the CDM group #A, OCCs of+1, +1, +1, and +1 may be applied to four REs in the frequency axis. Forthe DMRS antenna port #2 of the CDM group #A, OCCs of +1, −1, +1, and −1may be applied to four REs in the frequency axis. For the DMRS antennaport #3 of the CDM group #A, OCCs of +1, +1, −1, and −1 may be appliedto four REs in the frequency axis. For the DMRS antenna port #4 of theCDM group #A, OCCs of +1, −1, −1, and −1 may be applied to four REs inthe frequency axis.

Each CDM group may be repeated once of the (b), two times of (c), orthree times of the (d) in the (FIG. 7) within one PRB in the frequencyaxis.

As illustrated in (b) in the FIG. 7, when a DMRS mapping pattern isrepeated once within one PRB, DMRS overhead may be expressed as 1 RE per1 port and 1 PRB. That is, one CDM group is mapped onto a total of fourREs in one PRB, and four DMRS antenna ports are included in one CDMgroup and thus, it is expressed that one DMRS antenna port has overheadcorresponding to one RE.

The (b) in the FIG. 7 illustrates an example in which each CDM groupapplies a lengh-4 OCC-based CDM (i.e., CDM4) in the frequency axis withrespect to four contiguous or discontiguous REs in the frequency axiswithin one symbol, and repeats this once within one PRB in the frequencyaxis (i.e., four REs are used for four DMRS antenna ports within onePRB). A specific symbol index in a slot and a subcarrier position in aPRB for DMRS REs of (b) the FIG. 7 are not limited, and may bedetermined according to a previously fixed position or a positionobtained from signaling by a base station.

As illustrated in (c) in the FIG. 7, when a DMRS mapping pattern isrepeated two times within one PRB, DMRS overhead may be expressed as 2REs per 1 port and 1 PRB. That is, one CDM group is mapped onto a totalof eight REs in one PRB, and four DMRS antenna ports are included in oneCDM group and thus, it is expressed that one DMRS antenna port hasoverhead corresponding to two REs.

The (c) of the FIG. 7 illustrates an example in which each CDM groupapplies a lengh-4 OCC-based CDM (i.e., CDM4) in the frequency axis withrespect to four contiguous or discontinuous REs in the frequency axiswithin one symbol, and repeats this two times within one PRB in thefrequency axis (i.e., eight REs are used for four DMRS antenna portswithin one PRB). A specific symbol index in a slot and a subcarrierposition in a PRB for DMRS REs of (c) of the FIG. 7 are not limited, andmay be determined according to a previously fixed position or a positionobtained from signaling by a base station.

As illustrated in (d) in the FIG. 7, when a DMRS mapping pattern isrepeated three times within one PRB, DMRS overhead may be expressed as 3REs per 1 port and 1 PRB. That is, one CDM group is mapped onto a totalof 12 REs in one PRB, and four DMRS antenna ports are included in oneCDM group and thus, it is expressed that one DMRS antenna port hasoverhead corresponding to three REs.

The (d) in the FIG. 7 illustrates an example in which each CDM groupapplies a lengh-4 OCC-based CDM (i.e., CDM4) in the frequency axis withrespect to four contiguous or discontiguous REs in the frequency axiswithin one symbol, and repeats this three times within one PRB (i.e., 12REs are used for four DMRS antenna ports within one PRB). A specificsymbol index in a slot and a subcarrier position in a PRB for DMRS REsof (d) of the FIG. 7 are not limited, and may be determined according toa previously fixed position or a position obtained from signaling by abase station.

An additional DMRS may be mapped onto the rear part of the slot bytaking into consideration a high Doppler scenario, using the basicpatterns of (b) and (d) in the FIG. 7.

Particularly, the patterns onto which a DMRS is mapped in (b) and (d) inthe FIG. 7 (patterns indicating relative positions of REs onto which aDMRS is mapped in the time-frequency domain, excluding a specific symbolindex and a specific subcarrier index as illustrated in (a) in the FIG.2) may be defined as patterns 5-1, 5-2, and 5-3, respectively. Based onthe above, a DMRS according to a basic pattern may be mapped onto thefront part in one slot from the perspective of time, and a DMRSaccording to an additional pattern may be mapped onto the rear part inthe same slot, as shown in Table 15 provided below.

TABLE 15 DMRS pattern Basic pattern Additional pattern embodiments(front part of slot) (rear part of slot) 65 5-1 None 66 5-2 None 67 5-3None 68 5-1 5-1 69 5-1 5-2 70 5-1 5-3 71 5-2 5-1 72 5-2 5-2 73 5-2 5-374 5-3 5-1 75 5-3 5-2 76 5-3 5-3

The examples of (e) and (f) in the FIG. 7 may correspond to DMRS patternembodiments 74 and 76 of Table 15, respectively.

FIG. 8 is a diagram illustrating an additional example of a DMRS patternin one PRB according to the present disclosure.

The examples of FIG. 8 may correspond to detailed examples similar tothe DMRS pattern of (b) in the FIG. 2. That is, basically, in the DMRSpattern of FIG. 8, CDM groups #A, #B, and #C, which are distinguishedaccording to the FDM scheme, may be mapped onto a first symbol.Alternatively, basically, in the DMRS pattern of FIG. 8, CDM groups #A,#B, and #C, which are distinguished according to the FDM scheme, may bemapped onto a first symbol. CDM groups #A, #B, and #C, which aredistinguished according to the FDM scheme, may also be mapped onto asecond symbol. As described above, corresponding CDM groups may bemapped onto only the first symbol or may be mapped onto both the firstsymbol and the second symbol, according to overhead.

As an additional example, the CDM group #A may be mapped onto the firstsymbol, and the CDM group #C may be mapped onto the second symbol. TheCDM group #B may be mapped onto only the first symbol, or may be mappedonto both the first symbol and the second symbol, according to overhead.

The OCC mapping scheme will be described with reference to (a) in theFIG. 8.

As illustrated in the (a) in the FIG. 8, in all cases, with respect tofour REs in the frequency axis within one symbol to which correspondingCDM groups are mapped, a is applied to a first RE (e.g., an RE havingthe lowest subcarrier index) as an OCC value. b is applied to a secondRE (e.g., an RE having the second lowest subcarrier index) as an OCCvalue. c is applied to a third RE (e.g., an RE having the third lowestsubcarrier index) as an OCC value. d is applied to a fourth RE (e.g., anRE having the highest subcarrier index) as an OCC value.

The OCC values a, b, c, and d may be given as listed in Table 16provided below

TABLE 16 1st antenna 2nd antenna 3rd antenna 4th antenna port port portport OCC in each CDM in each CDM in each CDM in each CDM value groupgroup group group a +1 +1 +1 +1 b +1 −1 +1 −1 c +1 +1 −1 −1 d +1 −1 −1+1

For example, for the DMRS antenna port #1 of the CDM group #A, OCCs of+1, +1, +1, and +1 may be applied to four REs in the frequency axis. Forthe DMRS antenna port #2 of the CDM group #A, OCCs of +1, −1, +1, and −1may be applied to four REs in the frequency axis. For the DMRS antennaport #3 of the CDM group #A, OCCs of +1, +1, −1, and −1 may be appliedto four REs in the frequency axis. For the DMRS antenna port #4 of theCDM group #A, OCCs of +1, −1, −1, and −1 may be applied to four REs inthe frequency axis.

Each CDM group may be repeated once of (b), or two times of (c) in theFIG. 8 within a PRB in the frequency axis.

As illustrated in (b) in the FIG. 8, when a DMRS mapping pattern isrepeated once within one PRB, DMRS overhead may be expressed as 1 RE per1 port and 1 PRB. That is, one CDM group is mapped onto a total of fourREs in one PRB, and four DMRS antenna ports are included in one CDMgroup and thus, it is expressed that one DMRS antenna port has overheadcorresponding to one RE.

The (b) in the FIG. 8 illustrates an example in which each CDM groupapplies a lengh-4 OCC-based CDM (i.e., CDM4) in the frequency axis withrespect to four contiguous or discontiguous REs in the frequency axiswithin one symbol, and repeats this once within one PRB in the frequencyaxis (i.e., four REs are used for four DMRS antenna ports within onePRB). A specific symbol index in a slot and a subcarrier position in aPRB for DMRS REs of (b) in the FIG. 8 are not limited, and may bedetermined according to a previously fixed position or a positionobtained from signaling by a base station.

As illustrated in (c) in the FIG. 8, when a DMRS mapping pattern isrepeated two times within one PRB, DMRS overhead may be expressed as 2REs per 1 port and 1 PRB. That is, one CDM group is mapped onto a totalof eight REs in one PRB, and four DMRS antenna ports are included in oneCDM group and thus, it is expressed that one DMRS antenna port hasoverhead corresponding to two REs.

The (c) in the FIG. 8 illustrates an example in which each CDM groupapplies a lengh-4 OCC-based CDM (i.e., CDM4) in the frequency axis withrespect to four contiguous or discontiguous REs in the frequency axiswithin one symbol, and repeats this two times within one PRB in thefrequency axis (i.e., eight REs are used for four DMRS antenna portswithin one PRB). A specific symbol index in a slot and a specificsubcarrier in a PRB for DMRS REs of the (c) in the FIG. 8 are notlimited, and may be determined according to a previously fixed positionor a position obtained from signaling by a base station.

An additional DMRS may be mapped onto the rear part of the slot bytaking into consideration a high Doppler scenario, using the basicpatterns of the (b) and (c) in the FIG. 8.

Particularly, the patterns onto which a DMRS is mapped in the (b) and(c) in the FIG. 8 (patterns indicating relative positions of REs ontowhich a DMRS is mapped in the time-frequency domain, excluding aspecific symbol index and a specific subcarrier index as illustrated in(b) in the FIG. 2) may be defined as patterns 6-1 and 6-2, respectively.Based on the above, a DMRS according to a basic pattern may be mappedonto the front part in one slot from the perspective of time, and a DMRSaccording to an additional pattern may be mapped onto the part in thesame slot, as shown in Table 17 provided below.

TABLE 17 DMRS pattern Basic pattern Additional pattern embodiments(front part of slot) (rear part of slot) 77 6-1 None 78 6-2 None 79 6-16-1 80 6-1 6-2 81 6-2 6-1 82 6-2 6-2

The examples of (d) and (e) in the FIG. 8 may correspond to DMRS patternembodiments 81 and 82 of Table 17, respectively.

As an additional example, based on patterns 6-1 and 6-2, a DMRSaccording to the basic pattern is mapped onto the front part of one slotfrom the perspective of time, and DMRSs according to a first additionalpattern and a second additional pattern may be mapped onto the rear partof one slot.

TABLE 18 Basic pattern Second additional DMRS pattern (front part Firstadditional pattern pattern embodiments of slot) (rear part of slot)(rear part of slot) 83 6-1 None None 84 6-2 None None 85 6-1 6-1 None 866-1 6-2 None 87 6-2 6-1 None 88 6-2 6-2 None 89 6-1 6-1 6-1 90 6-1 6-16-2 91 6-1 6-2 6-1 92 6-1 6-2 6-2 93 6-2 6-1 6-1 94 6-2 6-1 6-2 95 6-26-2 6-1 96 6-2 6-2 6-2

The examples of (f) and (g) in the FIG. 8 may correspond to DMRS patternembodiments 93 and 96 of Table 18, respectively.

FIG. 9 is a diagram illustrating an additional example of a DMRS patternin one PRB according to the present disclosure.

The examples of FIG. 9 may correspond to detailed examples similar tothe DMRS pattern of (c) in the FIG. 2. That is, basically, in the DMRSpattern of FIG. 9, CDM groups #A and #B, which are distinguishedaccording to the FDM scheme, may be mapped onto a first symbol and asecond symbol. CDM group #C may be mapped onto a third symbol and afourth symbol.

The OCC mapping scheme will be described with reference to (a) in theFIG. 9.

As shown in the OCC mapping schemes A, B, C, and D in the (a) FIG. 9,mapping scheme case #1 and mapping scheme case #2 may be alternatelyapplied in the frequency axis with respect to a total of four REs in thefrequency axis and in the time axis in two symbols to whichcorresponding CDM groups are mapped. The OCC mapping at the first symbolof the case #1 may be the same as the OCC mapping at the second symbolof the case #2. The OCC mapping at the second symbol of the case #1 maybe the same as the OCC mapping at the first symbol of the case #2.

When the same OCC value (e.g., a and b) is mapped onto one symbol, powerbalancing problem may occur. Accordingly, as described above, the case#1and the case #2 are alternately applied in the frequency axis, so as toalternately map different OCC values (a and b, and c and d) onto onesymbol.

For example, in the case in which a CDM group is repeated C times in thefrequency axis with respect to two symbols to which corresponding CDMgroups are mapped, when the repetition indices are 0, 1, . . . , andC−1, the case #1 may be applied to an index corresponding toeven-numbered repetition, and the case #2 may be applied to an indexcorresponding to odd-numbered repetition.

The differences in the OCC mapping schemes A, B, C, and D will bedescribed from the perspective of the case #1. The OCC mapping scheme Amaps OCC values (a and b) in the time axis first, and then map OCCvalues (c and d) in the time axis at a subsequent frequency resource.The OCC mapping scheme B maps OCC values (a and b) in the frequency axisfirst, and then maps OCC values (c and d) in the frequency axis at asubsequent time resource. The OCC mapping scheme C maps OCC values (a,b, c, and d) clockwise from a time-and-frequency resource having thelowest index value. The OCC mapping scheme D maps OCC values (a, b, c,and d) counterclockwise from a time-and-frequency resource having thelowest index value.

The OCC values a, b, c, and d may be given as listed in Table 19provided below.

TABLE 19 1st antenna 2nd antenna 3rd antenna 4th antenna port port portport OCC in each CDM in each CDM in each CDM in each CDM value groupgroup group group a +1 +1 +1 +1 b +1 −1 +1 −1 c +1 +1 −1 −1 d +1 −1 −1+1

For example, for the DMRS antenna port #1 of the CDM group #A, OCCs of+1, +1, +1, and +1 may be applied to four REs in the frequency axis. Forthe DMRS antenna port #2 of the CDM group #A, OCCs of +1, −1, +1, and −1may be applied to four REs in the frequency axis. For the DMRS antennaport #3 of the CDM group #A, OCCs of +1, +1, −1, and −1 may be appliedto four REs in the frequency axis. For the DMRS antenna port #4 of theCDM group #A, OCCs of +1, −1, −1, and −1 may be applied to four REs inthe frequency axis.

Each CDM group may be repeated once of (b), two times of (c), or threetimes of (d) in the (FIG. 9) within one PRB in the frequency axis.

As illustrated in (b) in the FIG. 9, when a DMRS mapping pattern isrepeated once within one PRB, DMRS overhead may be expressed as 1 RE per1 port and 1 PRB. That is, one CDM group is mapped onto a total of fourREs in one PRB, and four DMRS antenna ports are included in one CDMgroup and thus, it is expressed that one DMRS antenna port has overheadcorresponding to one RE.

The (b) in the FIG. 9 illustrates an example in which each CDM groupapplies length-4 OCC-based CDM (i.e., CDM4) in the time axis and thefrequency axis with respect to a total of four REs disposed in twocontiguous or discontiguous subcarriers in each of two contiguous ordiscontiguous symbols, and repeats this once within one PRB in thefrequency axis (i.e., four REs are used for four DMRS antenna portswithin one PRB). A specific symbol index in a slot and a subcarrierposition in a PRB for DMRS REs of (b) in the FIG. 9 are not limited, andmay be determined according to a previously fixed position or a positionobtained from signaling by a base station.

As illustrated in (c) in the FIG. 9, when a DMRS mapping pattern isrepeated two times within one PRB, DMRS overhead may be expressed as 2REs per 1 port and 1 PRB. That is, one CDM group is mapped onto a totalof eight REs in one PRB, and four DMRS antenna ports are included in oneCDM group and thus, it is expressed that one DMRS antenna port hasoverhead corresponding to two REs.

The (c) in the FIG. 9 illustrates an example in which each CDM groupapplies length-4 OCC-based CDM (i.e., CDM4) in the time axis and thefrequency axis with respect to a total of four REs disposed in twocontiguous or discontiguous subcarriers in each of two contiguous ordiscontiguous symbols, and repeats this two times within one PRB in thefrequency axis (i.e., eight REs are used for four DMRS antenna portswithin one PRB). A specific symbol index in a slot and a subcarrierposition in one PRB for DMRS REs of (c) in the FIG. 9 are not limited,and may be determined according to a previously fixed position or aposition obtained from signaling by a base station.

As illustrated in (d) in the FIG. 9, when a DMRS mapping pattern isrepeated three times within one PRB, DMRS overhead may be expressed as 3REs per 1 port and 1 PRB. That is, one CDM group is mapped onto a totalof 12 REs in one PRB, and four DMRS antenna ports are included in oneCDM group and thus, it is expressed that one DMRS antenna port hasoverhead corresponding to three REs.

The (d) in the FIG. 9 illustrates an example in which each CDM groupapplies length-4 OCC-based CDM (i.e., CDM4) in the time axis withrespect to a total of four REs disposed in two contiguous ordiscontiguous subcarriers in each of two contiguous or discontiguoussymbols, and repeats this three times within one PRB in the frequencyaxis (i.e., 12 REs are used for four DMRS antenna ports within one PRB).A specific symbol index in a slot and a subcarrier position in a PRB forDMRS REs of (d) in the FIG. 9 are not limited, and may be determinedaccording to a previously fixed position or a position obtained fromsignaling by a base station.

An additional DMRS may be mapped onto the rear part of the slot bytaking into consideration a high Doppler scenario, using the basicpatterns of (b) and (d) in the FIG. 9.

Particularly, the patterns onto which a DMRS is mapped in the (b) and(d) in the FIG. 9 (patterns indicating relative positions of REs ontowhich a DMRS is mapped in the time-frequency domain, excluding aspecific symbol index and a specific subcarrier index as illustrated in(c) in the FIG. 2) may be defined as patterns 7-1, 7-2, and 7-3,respectively. Based on the above, a DMRS according to the basic patternmay be mapped onto the front part in one slot from the perspective oftime, and a DMRS according to an additional pattern may be mapped ontothe rear part in the same slot, as shown in Table 20 provided below.

TABLE 20 DMRS pattern Basic pattern Additional pattern embodiments(front part of slot) (rear part of slot) 97 7-1 None 98 7-2 None 99 7-3None 100 7-1 7-1 101 7-1 7-2 102 7-1 7-3 103 7-2 7-1 104 7-2 7-2 105 7-27-3 106 7-3 7-1 107 7-3 7-2 108 7-3 7-3

The examples of (e) and (f) in the FIG. 9 may correspond to DMRS patternembodiments 106 and 108 of Table 20, respectively.

FIG. 10 is a diagram illustrating an additional example of a DMRSpattern in one PRB according to the present disclosure.

The examples of FIG. 10 may correspond to detailed examples similar tothe DMRS pattern of (d) in the FIG. 2. That is, basically, in the DMRSpattern of FIG. 10, CDM groups #A, #B, and #C which are distinguishedaccording to the FDM scheme, may be mapped onto a first symbol and asecond symbol.

The OCC mapping scheme will be described with reference to (a) in theFIG. 10.

As shown in the OCC mapping schemes A, B, C, and D in (a) in the FIG.10, mapping scheme case #1 and mapping scheme case #2 may be alternatelyapplied in the frequency axis with respect to a total of four REs in thefrequency axis and in the time axis in two symbols to whichcorresponding CDM groups are mapped. The OCC mapping at the first symbolof the case #1 may be the same as the OCC mapping at the second symbolof the case #2. The OCC mapping at the second symbol of the case #1 maybe the same as the OCC mapping at the first symbol of the case #2.

When the same OCC value (e.g., a and b) is mapped onto one symbol, powerbalancing problem may occur. Accordingly, as described above, the case#1and the case #2 are alternately applied in the frequency axis, so as toalternately map different OCC values (a and b, and c and d) onto onesymbol.

For example, in the case in which a CDM group is repeated C times in thefrequency axis with respect to two symbols to which corresponding CDMgroups are mapped, when the repetition indices are 0, 1, . . . , andC−1, the case #1 may be applied to an index corresponding toeven-numbered repetition, and the case #2 may be applied to an indexcorresponding to odd-numbered repetition.

The differences in the OCC mapping schemes A, B, C, and D will bedescribed from the perspective of the case #1. The OCC mapping scheme Amaps OCC values (a and b) in the time axis first, and then maps OCCvalues (c and d) in the time axis at a subsequent frequency resource.The OCC mapping scheme B maps OCC values (a and b) in the frequency axisfirst, and then maps OCC values (c and d) in the frequency axis at asubsequent time resource. The OCC mapping scheme C maps OCC values (a,b, c, and d) clockwise from the RE “a” (where time-and-frequencyresource having the lowest index value). The OCC mapping scheme D mapsOCC values (a, b, c, and d) counterclockwise from a time-and-frequencyresource having the lowest index value.

The OCC values a, b, c, and d may be given as listed in Table 21provided below.

TABLE 21 1st antenna 2nd antenna 3rd antenna 4th antenna port in port inport in port in each CDM each CDM each CDM each CDM OCC value groupgroup group group a +1 +1 +1 +1 b +1 −1 +1 −1 c +1 +1 −1 −1 d +1 −1 −1+1

For example, for the DMRS antenna port #1 of the CDM group #A, OCCs of+1, +1, +1, and +1 may be applied to four Res (a, b, c, d) in thefrequency axis. For the DMRS antenna port #2 of the CDM group #A, OCCsof +1, −1, +1, and −1 may be applied to the four REs in the frequencyaxis. For the DMRS antenna port #3 of the CDM group #A, OCCs of +1, +1,−1, and −1 may be applied to the four REs in the frequency axis. For theDMRS antenna port #4 of the CDM group #A, OCCs of +1, −1, −1, and −1 maybe applied to the four REs in the frequency axis.

Each CDM group may be repeated once of (b), or two times of (c) in the(FIG. 10) within one PRB in the frequency axis.

As illustrated in (b) in the FIG. 10, when a DMRS mapping pattern isrepeated once within one PRB, DMRS overhead may be expressed as 1 RE per1 port and 1 PRB. That is, one CDM group is mapped onto a total of fourREs in one PRB, and four DMRS antenna ports are included in one CDMgroup and thus, it is expressed that one DMRS antenna port has overheadcorresponding to one RE.

The (b) of the FIG. 10 illustrates an example in which each CDM groupapplies length-4 OCC-based CDM (i.e., CDM4) in the time axis withrespect to a total of four REs disposed in two contiguous ordiscontiguous subcarriers in each of two contiguous or discontiguoussymbols, and repeats this once within one PRB in the frequency axis(i.e., four REs are used for four DMRS antenna ports within one PRB). Aspecific symbol index in a slot and a subcarrier position in a PRB forDMRS REs of (b) in the FIG. 10 are not limited, and may be determinedaccording to a previously fixed position or a position obtained fromsignaling by a base station.

As illustrated in (c) in the FIG. 10, when a DMRS mapping pattern isrepeated two times within one PRB, DMRS overhead may be expressed as 2REs per 1 port and 1 PRB. That is, one CDM group is mapped onto a totalof eight REs in one PRB, and four DMRS antenna ports are included in oneCDM group and thus, it is expressed that one DMRS antenna port hasoverhead corresponding to two REs.

The (c) of the FIG. 10 illustrates an example in which each CDM groupapplies length-4 OCC-based CDM (i.e., CDM4) in the time axis withrespect to a total of four REs disposed in two contiguous ordiscontiguous subcarriers in each of two contiguous or discontiguoussymbols, and repeats this two times within one PRB in the frequency axis(i.e., eight REs are used for four DMRS antenna ports within one PRB). Aspecific symbol index in a slot and a subcarrier position in a PRB forDMRS REs of (c) of the FIG. 10 are not limited, and may be determinedaccording to a previously fixed position or a position obtained fromsignaling by a base station.

An additional DMRS may be mapped onto the rear part(additional part) ofthe slot by taking into consideration a high Doppler shift scenario,using the basic patterns of the (b) and (c) in the FIG. 10.

Particularly, the patterns onto which a DMRS is mapped in the (b) and(c) in the FIG. 10 (patterns indicating relative positions of REs ontowhich a DMRS is mapped in the time-frequency domain, excluding aspecific symbol index and a specific subcarrier index as illustrated in(d) in the FIG. 2) may be defined as patterns 8-1 and 8-2, respectively.Based on the above, a DMRS according to a basic pattern may be mappedonto the front part in one slot from the perspective of time, and a DMRSaccording to an additional pattern may be mapped onto the rear part inthe same slot, as shown in Table 22 provided below.

TABLE 22 Basic pattern Additional pattern DMRS patterns (front part ofslot) (rear part of slot) 109 8-1 None 110 8-2 None 111 8-1 8-1 112 8-18-2 113 8-2 8-1 114 8-2 8-2

The examples of (d) and (e) in the FIG. 10 may correspond to DMRSpattern embodiments 113 and 114 of Table 22, respectively.

As an additional example, based on patterns 8-1 and 8-2, a DMRSaccording to the basic pattern is mapped onto the front part of one slotfrom the perspective of time, DMRSs according to a first additionalpattern and a second additional pattern may be mapped onto the rear partof one slot, as shown in Table 23 provided below.

TABLE 23 First additional Second additional DMRS pattern Basic patternpattern pattern embodiments (front part of slot) (rear part of slot)(rear part of slot) 115 8-1 None None 116 8-2 None None 117 8-1 8-1 None118 8-1 8-2 None 119 8-2 8-1 None 120 8-2 8-2 None 121 8-1 8-1 8-1 1228-1 8-1 8-2 123 8-1 8-2 8-1 124 8-1 8-2 8-2 125 8-2 8-1 8-1 126 8-2 8-18-2 127 8-2 8-2 8-1 128 8-2 8-2 8-2

The examples of (f) and (g) in the FIG. 10 may correspond to DMRSpattern embodiments 125 and 128 of Table 23, respectively.

In the above-described DMRS pattern embodiments, DMRS patterns may bedetermined according to whether the DMRS antenna overhead is 1 RE per 1port and 1 PRB, 2 REs per 1 port and 1 PRB, and 3 REs per 1 port and 1PRB in the case in which a total of 12 DMRS antenna ports are dividedinto a maximum of six or three CDM groups. Also, an additional patternmay be applied to one slot.

Hereinafter, a method of indicating a DMRS pattern, that is, a method ofsignaling DMRS pattern configuration information to a terminal by a basestation will be described according to embodiments of the presentdisclosure.

Factors that need to be taken into consideration in order to indicate aDMRS pattern may include: i) basic pattern overhead (includinginformation associated with the existence of a basic pattern); ii)additional pattern overhead (including information associated with theexistence of an additional pattern); iii) the position of an RE in aslot of the basic pattern (i.e., a symbol position and/or a subcarrierposition); iv) the position of an RE in a slot of the additional pattern(i.e., a symbol position and/or a subcarrier position); and v) virtualcell identification.

First, the method of signaling i) basic pattern overhead will bedescribed.

A DMRS may be transmitted together in a slot in which a physical channelthat requires demodulation is transmitted. However, when DMRS bundlingis applied in the time domain, there may exist a slot in which aphysical channel is transmitted and a basic DMRS pattern does not exist.DMRS bundling indicates a scheme of demodulating a physical channel inmultiple slots based on channel information estimated using a DMRStransmitted in one of the multiple slots.

For example, as illustrated in FIGS. 3, 5, 7, and 9, basic DMRS patternoverhead may be signaled using 1-bit information. For example, the casein which a basic DMRS pattern does not exist, or the case in which abasic DMRS pattern has the maximum overhead when the basic DMRS patternexists may be indicated. For example, a bit value of 0 may indicate thatthe DMRS overhead is 0 (zero) (i.e., a DMRS does not exist in acorresponding slot). A bit value of 1 may indicate that the basicpattern DMRS overhead is 3 (i.e., a CDM group of the basic pattern isrepeated three times in one PRB).

As an additional example, as illustrated in FIGS. 4, 6, 8, and 10, basicDMRS pattern overhead may be signaled using 1-bit information. Forexample, the case in which a basic DMRS pattern does not exist, or thecase in which a basic DMRS pattern has the maximum overhead when thebasic DMRS pattern exists may be indicated. For example, a bit value of0 may indicate that the DMRS overhead is 0 (zero) (i.e., the fact that aDMRS does not exist in a corresponding slot). A bit value of 1 mayindicate that the basic pattern DMRS overhead is 2 (i.e., a CDM group ofthe basic pattern is repeated two times in one PRB).

As another example, as illustrated in FIGS. 3, 5, 7, and 9, basic DMRSpattern overhead may be signaled using 2-bit information. For example,the fact that a basic DMRS pattern does not exist, or a specific DMRSoverhead value may be indicated. For example, a bit value of 0 mayindicate that the DMRS overhead is 0 (zero) (i.e., the fact that a DMRSdoes not exist in a corresponding slot). A bit value of 1 may indicatethat the basic pattern DMRS overhead is 1 (i.e., a CDM group of thebasic pattern is repeated once in one PRB). A bit value of 2 mayindicate that the basic pattern DMRS overhead is 2 (i.e., a CDM group ofthe basic pattern is repeated two times in one PRB). A bit value of 3may indicate that the basic pattern DMRS overhead is 3 (i.e., a CDMgroup of the basic pattern is repeated three times in one PRB).

As an additional example, as illustrated in FIGS. 4, 6, 8, and 10, basicDMRS pattern overhead may be signaled using 2-bit information. Forexample, the fact that a basic DMRS pattern does not exist, or aspecific DMRS overhead value may be indicated. For example, a bit valueof 0 may indicate that the DMRS overhead is 0 (zero) (i.e., the factthat a DMRS does not exist in a corresponding slot). A bit value of 1may indicate that the basic DMRS pattern overhead is 1 (i.e., a CDMgroup of the basic pattern is repeated once in one PRB). A bit value of2 may indicate that the basic DMRS pattern overhead is 2 (i.e., a CDMgroup of the basic pattern is repeated two times in one PRB). A bitvalue of 3 may be reserved.

Subsequently, the method of signaling ii) additional pattern overheadwill be described.

When a basic DMRS pattern does not exist in a slot, an additionalpattern may also not exist in the slot. Also, when a high Dopplerscenario is not taken into consideration, an additional pattern may notexist in a slot in which a basic DMRS pattern exists.

For example, as illustrated in FIGS. 3, 5, 7, and 9, additional DMRSpattern overhead may be signaled using 1-bit information. For example,the case in which an additional DMRS pattern does not exist, or the casein which an additional DMRS pattern has the maximum overhead when theadditional DMRS pattern exists may be indicated. For example, a bitvalue of 0 may indicate that the additional DMRS pattern overhead is 0(zero) (i.e., the fact that an additional DMRS pattern does not exist ina corresponding slot). A bit value of 1 may indicate that the additionalDMRS pattern overhead is 3 (i.e., a CDM group of the additional patternis repeated three times in one PRB).

As an additional example, as illustrated in FIGS. 4, 6, 8, and 10,additional DMRS pattern overhead may be signaled using 1-bitinformation. For example, the case in which an additional DMRS patterndoes not exist, or the case in which an additional DMRS pattern has themaximum overhead when the additional DMRS pattern exists may beindicated. For example, a bit value of 0 may indicate that theadditional DMRS pattern overhead is 0 (zero) (i.e., a first additionalDMRS pattern and a second additional DMRS pattern do not exist in acorresponding slot). A bit value of 1 may indicate that the firstadditional DMRS pattern overhead is 2 (i.e., a CDM group of the firstadditional pattern is repeated two times in one PRB) and that the secondadditional DMRS pattern overhead is 2 (i.e., a CDM group of the secondadditional pattern is repeated two times in one PRB).

As another example, as illustrated in FIGS. 3, 5, 7, and 9, additionalDMRS pattern overhead may be signaled using 2-bit information. Forexample, the fact that an additional DMRS pattern does not exist, or aspecific additional DMRS pattern overhead value may be indicated. Forexample, a bit value of 0 may indicate that the additional DMRS patternoverhead is 0 (zero) (i.e., the fact that an additional DMRS patterndoes not exist in a corresponding slot). A bit value of 1 may indicatethat the additional DMRS pattern overhead is 1 (i.e., a CDM group of theadditional pattern is repeated once in one PRB). A bit value of 2 mayindicate that the additional pattern DMRS overhead is 2 (i.e., a CDMgroup of the additional pattern is repeated two times in one PRB). A bitvalue of 3 may indicate that the additional DMRS pattern overhead is 3(i.e., a CDM group of the additional pattern is repeated three times inone PRB).

As an additional example, as illustrated in FIGS. 4, 6, 8, and 10,additional DMRS pattern overhead may be signaled using 3-bitinformation. For example, the fact that an additional DMRS pattern doesnot exist, or a specific additional DMRS pattern overhead value may beindicated. For example, a bit value of 0 may indicate that theadditional DMRS pattern overhead is 0 (zero) (i.e., a first additionalDMRS pattern and a second additional DMRS pattern do not exist in acorresponding slot). A bit value of 1 may indicate that the firstadditional DMRS pattern overhead is 1 (i.e., a CDM group of the firstadditional pattern is repeated once in one PRB) and that the secondadditional DMRS pattern overhead is 0 (i.e., the second additional DMRSpattern does not exist in a corresponding slot). A bit value of 2 mayindicate that the first additional DMRS pattern overhead is 2 (i.e., aCDM group of the first additional pattern is repeated two times in onePRB) and that the second additional DMRS pattern overhead is 0 (i.e.,the second additional DMRS pattern does not exist in a correspondingslot). A bit value of 3 may indicate that the first additional DMRSpattern overhead is 1 (i.e., a CDM group of the first additional patternis repeated once in one PRB) and that the second additional DMRS patternoverhead is 1 (i.e., a CDM group of the second additional pattern isrepeated once in one PRB). A bit value of 4 may indicate that the firstadditional DMRS pattern overhead is 2 (i.e., a CDM group of the firstadditional pattern is repeated two times in one PRB) and that the secondadditional DMRS pattern overhead is 2 (i.e., a CDM group of the secondadditional pattern is repeated once in one PRB). A bit value of 5 mayindicate that the first additional DMRS pattern overhead is 2 (i.e., aCDM group of the first additional pattern is repeated two times in onePRB) and that the second additional DMRS pattern overhead is 2 (i.e., aCDM group of the second additional pattern is repeated two times in onePRB). A bit value of 6 and a bit value of 7 may be reserved.

The above-described example assumes the case in which the secondadditional pattern overhead is set to be less than or equal to the firstadditional pattern overhead (i.e., the second additional patternoverhead is set not to be higher than the first additional patternoverhead). When it is assumed that the second additional patternoverhead is always 0, the first additional pattern overhead may beindicated using only bit values of 0, 1, and 2.

As another example, as illustrated in FIGS. 3, 5, 7, and 9, additionalDMRS pattern overhead may be signaled using 1-bit information. Forexample, the case in which an additional DMRS pattern does not exist, orthe case in which an additional DMRS pattern has predetermined overheadas opposed to the maximum overhead when the additional DMRS patternexists may be indicated. For example, a bit value of 0 may indicate thatthe additional DMRS pattern overhead is 0 (zero) (i.e., the fact that anadditional DMRS pattern does not exist in a corresponding slot). A bitvalue of 1 may indicate that the additional DMRS pattern overhead is 2(i.e., a CDM group of the additional pattern is repeated two times inone PRB).

As an additional example, as illustrated in FIGS. 4, 6, 8, and 10,additional DMRS pattern overhead may be signaled using 1-bitinformation. For example, the case in which an additional DMRS patterndoes not exist, or the case in which an additional DMRS pattern haspredetermined overhead as opposed to the maximum overhead when theadditional DMRS pattern exists may be indicated. For example, a bitvalue of 0 may indicate that the additional DMRS pattern overhead is 0(zero) (i.e., a first additional DMRS pattern and a second additionalDMRS pattern do not exist in a corresponding slot). A bit value of 1 mayindicate that the first additional DMRS pattern overhead is 1 (i.e., aCDM group of the first additional pattern is repeated once in one PRB)and that the second additional DMRS pattern overhead is 1 (i.e., a CDMgroup of the second additional pattern is repeated once in one PRB).

As another example, as illustrated in FIGS. 3, 5, 7, and 9, additionalDMRS pattern overhead may be signaled using 1-bit information. Forexample, the case in which an additional DMRS pattern does not exist, orthe case in which an additional DMRS pattern has predetermined overheadas opposed to the maximum overhead when the additional DMRS patternexists may be indicated. For example, a bit value of 0 may indicate thatthe additional DMRS pattern overhead is 0 (zero) (i.e., the fact that anadditional DMRS pattern does not exist in a corresponding slot). A bitvalue of 1 may indicate that the additional DMRS pattern overhead is 1(i.e., a CDM group of the additional pattern is repeated once in onePRB).

As an additional example, as illustrated in FIGS. 4, 6, 8, and 10,additional DMRS pattern overhead may be signaled using 1-bitinformation. For example, the case in which an additional DMRS patterndoes not exist, or the case in which an additional DMRS pattern haspredetermined overhead as opposed to the maximum overhead when theadditional DMRS pattern exists may be indicated. For example, a bitvalue of 0 may indicate that the additional DMRS pattern overhead is 0(zero) (i.e., a first additional DMRS pattern and a second additionalDMRS pattern do not exist in a corresponding slot). A bit value of 1 mayindicate that the first additional DMRS pattern overhead is 1 (i.e., aCDM group of the first additional pattern is repeated once in one PRB)and that the second additional DMRS pattern overhead is 0 (i.e., thesecond additional pattern does not exist).

Subsequently, the method of signaling iii) the position of an RE (i.e.,a symbol position and/or a subcarrier position) in a slot of a basicpattern will be described.

In order to signal an RE position of a basic pattern, candidatepositions onto which a basic DMRS pattern may be mapped, may bedetermined in consideration of the position of a control region in theslot (i.e., an RE position to which a control channel is mapped), basicDMRS pattern overhead, the position of a data region in the slot (i.e.,an RE position onto which a data channel is mapped), and the like. Aposition that is used from among the candidate positions may besignaled. In the case in which the number of candidate positions is 1, aterminal may be aware of an RE position even though the RE position ofthe basic pattern is not signaled. The RE position of the basic patternmay be indicated based on a symbol index value and/or a subcarrier indexvalue.

Subsequently, the method of signaling iv) the position of an RE (i.e., asymbol position and/or a subcarrier position) in a slot of an additionalpattern will be described.

In order to signal an RE position of an additional pattern, candidatepositions onto which an additional DMRS pattern may be mapped, may bedetermined in consideration of the position of a basic DMRS pattern,additional pattern overhead, the position of a data region (e.g., theposition and the transmission interval of a downlink data channel in aTime Division Duplex (TDD) mode), and the like. A position that is usedfrom among the candidate positions may be signaled. In the case in whichthe number of candidate positions is 1, a terminal may be aware of an REposition even though the RE position of the basic pattern is notsignaled. The RE position of the basic pattern may be indicated based ona symbol index value and/or a subcarrier index value, and may be definedas a relative value determined based on the position the basic pattern.

Subsequently, the method of signaling v) virtual cell identificationwill be described.

Unlike the physical ID of a cell, virtual cell ID (VCID) may be set toperform coordinated transmission with another cell (e.g., CoordinatedMulti-Point (CoMP) transmission). Two VCIDs or three or more VCIDs maybe set. For example, VCID for Transmission Reception Points (TRPs) thatperform operation by sharing the same cell-specific ID or the samegroup-specific ID when operating as CoMP, VCID for TRPs that performoperation based on different cell-specific IDs or differentgroup-specific IDs when operating as CoMP or not, or the like may beset. In this instance, a base station may report a VCID value to be usedwhen a terminal receives a DMRS (i.e., a VCID value used as an initialvalue for generating a DMRS sequence or the like). Also, VCID is not afactor that is directly associated with DMRS pattern configuration.However, the values of the DMRS pattern configuration factors i) to iv)may be set based on VCID (when DMRS pattern configuration is set foreach terminal in MU-MIMO environment, the same VCID may be configuredfor the terminals operating in MU-MIMO), VCID may be considered as afactor that is indirectly associated with DMRS pattern configuration.

Hereinafter, the method of signaling DMRS pattern configurationinformation will be described.

As an example of the signaling method, the factors of the DMRSconfiguration information such as i) to v) may be separately orindependently signaled.

For example, configuration information associated with i) basic patternoverhead (including information indicating the existence of a basicpattern) may be dynamically indicated in the state of being explicitlyor implicitly included in downlink control information (DCI) or thelike. Alternatively, the configuration information associated with i)basic pattern overhead (information indicating the existence of a basicpattern) may be semi-statically indicated in the state of beingexplicitly or implicitly included in a higher layer signaling (e.g.,Radio Resource Control (RRC) layer signaling or the like).

For example, configuration information associated with ii) additionalpattern overhead (information indicating the existence of an additionalpattern) may be dynamically indicated in the state of being explicitlyor implicitly included in DCI or the like. Alternatively, theconfiguration information associated with ii) additional patternoverhead (information information the existence of an additionalpattern) may be semi-statically indicated in the state of beingexplicitly or implicitly included in higher layer signaling (e.g., RRCsignaling or the like).

For example, iii) an RE position in a slot of a basic pattern (i.e., asymbol position and/or a subcarrier position) may be previously definedas a fixed value, and may not be signaled separately. Alternatively, theconfiguration information associated with iii) an RE position in a slotof a basic pattern (i.e., a symbol position and/or a subcarrierposition) may be dynamically indicated in the state of being explicitlyor implicitly included in DCI or the like. Alternatively, theconfiguration information associated with iii) an RE position in a slotof a basic pattern (i.e., a symbol position and/or a subcarrierposition) may be semi-statically indicated in the state of beingexplicitly or implicitly included in higher layer signaling (e.g., RRCsignaling or the like).

For example, iv) an RE position in a slot of an additional pattern(i.e., a symbol position and/or a subcarrier position) may be previouslydefined as a fixed value, and may not be signaled separately.Alternatively, the configuration information associated with iv) an REposition in a slot of an additional pattern (i.e., a symbol positionand/or a subcarrier position) may be dynamically indicated in the stateof being explicitly or implicitly included in DCI or the like.Alternatively, the configuration information associated with iv) an REposition in a slot of an additional pattern (i.e., a symbol positionand/or a subcarrier position) may be semi-statically indicated in thestate of being explicitly or implicitly included in higher layersignaling (e.g., RRC signaling or the like).

For example, configuration information associated with v) virtual cellidentification may be dynamically indicated in the state of beingexplicitly or implicitly included in DCI or the like. Alternatively, theconfiguration information associated with v) virtual cell identification(VCID) may be semi-statically indicated in the state of being explicitlyor implicitly included in higher layer signaling (e.g., RRC signaling orthe like).

In the case of signaling DMRS pattern configuration information usingDCI or the like among the above-described examples, the DMRS patternconfiguration information may be immediately and dynamically signaledwhen needed. However, when the amount of information included in the DCIis changed or increased, the whole system throughput may deteriorate.Alternatively, in the case of signaling DMRS pattern configurationinformation using RRC signaling or the like, even when the amount ofinformation included in RRC signaling is increased, serious problems,such as deterioration of system throughput, does not occur. However, theDMRS pattern configuration information may not be immediately signaledwhen needed.

As an additional example of the signaling method, two or more of thefactors of the DMRS configuration information such as i) to v) may besignaled in the manner of joint encoding. That is, signaling setcandidates determined in consideration of two or more of the factors ofthe DMRS configuration information may be set via higher layersignaling, and one of the signaling set candidates may be indicated viaDCI.

The method of semi-statically setting signaling set candidates viahigher layer signaling may be based on the descriptions for each of thefactors of the DMRS configuration information such as i) to v).

Also, one of the multiple signaling set candidates may be dynamicallyindicated via a 1-bit indicator or 2-bit indicator included in DCI.

Also, in regard to a factor that is not included in a signaling setcandidate from among the factors of the DMRS configuration informationsuch as i) to v), a separate or independent signaling method may beapplied as described above.

Embodiment 1

The present embodiment describes a method of setting signaling setcandidates including factors: i) basic pattern overhead (includinginformation indicating the existence of a basic pattern; ii) additionalpattern overhead (including information indicating the existence of anadditional pattern); and v) virtual cell identification. One of thecandidates may be dynamically indicated using 1-bit information or 2-bitinformation included in DCI.

Table 24 provided below shows an example of dynamically indicating DMRSpattern configuration information using 1-bit information included inDCI.

TABLE 24 RRC RRC RRC DCI bit value parameter #A parameter #B parameter#C 0 basic DMRS pattern additional DMRS pattern VCID #1 (RRC setcandidate #1) overhead #1 overhead #1 1 basic DMRS pattern additionalDMRS pattern VCID #2 (RRC set candidate #2) overhead #2 overhead #2

In the example of Table 24, basic DMRS pattern overhead #1 and basicDMRS pattern overhead #2 may be respectively set via RRC signaling asdescribed in the method of signaling basic pattern overhead. The basicDMRS pattern overhead #1 and the basic DMRS pattern overhead #2 may beset as the same value or different values.

As described in the method of signaling ii) additional pattern overhead,additional DMRS pattern overhead #1 and additional DMRS pattern overhead#2 may be respectively set via RRC signaling. The additional DMRSpattern overhead #1 and the additional DMRS pattern overhead #2 may beset as the same value or different values.

As described in the method of signaling v) virtual cell identification,VCID #1 and VCID #2 may be respectively set via RRC signaling. The VCID#1 and the VCID #2 may be set as the same value or different values.

Table 25 provided below shows an example of dynamically indicating DMRSpattern configuration information using 2-bit information included inDCI.

TABLE 25 RRC RRC RRC DCI bit value parameter #A parameter #B parameter#C 0 basic DMRS pattern additional DMRS VCID #1 (RRC set candidate #1)overhead #1 pattern overhead #1 1 basic DMRS pattern additional DMRSVCID #2 (RRC set candidate #2) overhead #2 pattern overhead #2 2 basicDMRS pattern additional DMRS VCID #3 (RRC set candidate #3) overhead #3pattern overhead #3 3 basic DMRS pattern additional DMRS VCID #4 (RRCset candidate #4) overhead #4 pattern overhead #4

In the example of Table 25, basic DMRS pattern overhead #1, #2, #3, and#4 may be respectively set via RRC signaling as described in the methodof signaling basic pattern overhead. The basic DMRS pattern overhead #1,#2, #3, and #4 may be set as different values, or some or all of thebasic DMRS pattern overhead #1, #2, #3, and #4 may be set as the samevalue.

As described in the method of signaling ii) additional pattern overhead,additional DMRS pattern overhead #1, #2, #3, and #4 may be respectivelyset via RRC signaling. The additional DMRS pattern overhead #1, #2, #3,and #4 may be set as different values, or some or all of the additionalDMRS pattern overhead #1, #2, #3, and #4 may be set as the same value.

As described in the method of signaling v) virtual cell identification,VCIDs #1, #2, #3, and #4 may be respectively set via RRC signaling. TheVCIDs #1, #2, #3, and #4 may be set as different values, or some or allof the VCIDs #1, #2, #3, and #4 may be set as the same value.

Each of iii) an RE position (i.e., a symbol position and/or a subcarrierposition) in a slot of a basic pattern and iv) an RE position (i.e., asymbol position and/or a subcarrier position) in a slot of an additionalpattern, which are not included in a higher layer signaling setcandidate, may be separately or independently set via DCI or RRCsignaling.

Embodiment 2

The present embodiment describes a method of setting signaling setcandidates including factors: i) basic pattern overhead (includinginformation indicating the existence of a basic pattern); and ii)additional pattern overhead (including information indicating theexistence of an additional pattern). One of the candidates may bedynamically indicated using 1-bit information or 2-bit informationincluded in DCI.

Table 26 provided below shows an example of dynamically indicating DMRSpattern configuration information using 1-bit information included inDCI.

TABLE 26 RRC RRC DCI bit value parameter #A parameter #B 0 basic DMRSpattern additional DMRS pattern (RRC set candidate #1) overhead #1overhead #1 1 basic DMRS pattern additional DMRS pattern (RRC setcandidate #2) overhead #2 overhead #2

In the example of Table 26, basic DMRS pattern overhead #1 and basicDMRS pattern overhead #2 may be respectively set via RRC signaling asdescribed in the method of signaling i) basic pattern overhead. Thebasic DMRS pattern overhead #1 and the basic DMRS pattern overhead #2may be set as the same value or different values.

As described in the method of signaling ii) additional pattern overhead,additional DMRS pattern overhead #1 and additional DMRS pattern overhead#2 may be respectively set via RRC signaling. The additional DMRSpattern overhead #1 and the additional DMRS pattern overhead #2 may beset as the same value or different values.

Table 27 provided below shows an example of dynamically indicating DMRSpattern configuration information using 2-bit information included inDCI.

TABLE 27 RRC RRC DCI bit value parameter #A parameter #B 0 basic DMRSpattern additional DMRS pattern (RRC set candidate #1) overhead #1overhead #1 1 basic DMRS pattern additional DMRS pattern (RRC setcandidate #2) overhead #2 overhead #2 2 basic DMRS pattern additionalDMRS pattern (RRC set candidate #3) overhead #3 overhead #3 3 basic DMRSpattern additional DMRS pattern (RRC set candidate #4) overhead #4overhead #4

In the example of Table 27, basic DMRS pattern overhead #1, #2, #3, and#4 may be respectively set via RRC signaling as described in the methodof signaling i) basic pattern overhead. The basic DMRS pattern overhead#1, #2, #3, and #4 may be set as different values, or some or all of thebasic DMRS pattern overhead #1, #2, #3, and #4 may be set as the samevalue.

As described in the method of signaling ii) additional pattern overhead,additional DMRS pattern overhead #1, #2, #3, and #4 may be respectivelyset via RRC signaling. The additional DMRS pattern overhead #1, #2, #3,and #4 may be set as different values, or some or all of the additionalDMRS pattern overhead #1, #2, #3, and #4 may be set as the same value.

Each of iii) an RE position in a slot of a basic pattern (i.e., a symbolposition and/or a subcarrier position), iv) an RE position in a slot ofan additional pattern (i.e., a symbol position and/or a subcarrierposition), and v) virtual cell identification, which are not included ina higher layer signaling set candidate, may be separately orindependently set via DCI or RRC signaling.

Embodiment 3

The present embodiment describes a method of setting signaling setcandidates including factors: i) basic pattern overhead (includinginformation indicating the existence of a basic pattern); ii) additionalpattern overhead (including information indicating the existence of anadditional pattern); iii) an RE position (i.e., a symbol position and/ora subcarrier position) in a slot of the basic pattern; iv) an REposition (i.e., a symbol position and/or a subcarrier position) in aslot of the additional pattern; and v) virtual cell identification. Oneof the candidates may be dynamically indicated using 1-bit informationor 2-bit information included in DCI.

Table 28 provided below shows an example of dynamically indicating DMRSpattern configuration information using 1-bit information included inDCI.

TABLE 28 RRC RRC RRC RRC RRC DCI bit value parameter #A parameter #Bparameter #C parameter #D parameter #E 0 basic DMRS additional VCID #1basic additional (RRC set pattern DMRS pattern DMRS pattern DMRS patterncandidate #1) overhead #1 overhead #1 position #1 position #1 1 basicDMRS additional VCID #2 basic additional (RRC set pattern DMRS patternDMRS pattern DMRS pattern candidate #2) overhead #2 overhead #2 position#2 position #2

In the example of Table 28, basic DMRS pattern overhead #1 and basicDMRS pattern overhead #2 may be respectively set via RRC signaling asdescribed in the method of signaling i) basic pattern overhead. Thebasic DMRS pattern overhead #1 and the basic DMRS pattern overhead #2may be set as the same value or different values.

As described in the method of signaling ii) additional pattern overhead,additional DMRS pattern overhead #1 and additional DMRS pattern overhead#2 may be respectively set via RRC signaling. The additional DMRSpattern overhead #1 and the additional DMRS pattern overhead #2 may beset as the same value or different values.

As described in the method of signaling iii) an RE position (i.e., asymbol position and/or a subcarrier position) in a slot of a basicpattern, each of the basic DMRS pattern position #1 and the basic DMRSpattern position #2 may be respectively set via RRC signaling. The basicDMRS pattern position #1 and the basic DMRS pattern position #2 may beset as the same value or different values.

As described in the method of signaling iv) an RE position (i.e., asymbol position and/or a subcarrier position) in a slot of an additionalpattern, each of the additional DMRS pattern position #1 and theadditional DMRS pattern position #2 may be respectively set via RRCsignaling. The additional DMRS pattern position #1 and the additionalDMRS pattern position #2 may be set as the same value or differentvalues.

As described in the method of signaling v) virtual cell identification,VCID #1 and VCID #2 may be respectively set via RRC signaling. The VCID#1 and the VCID #2 may be set as the same value or different values.

Table 29 provided below shows an example of dynamically indicating DMRSpattern configuration information using 2-bit information included inDCI.

TABLE 29 RRC RRC RRC RRC RRC DCI bit value parameter #A parameter #Bparameter #C parameter #D parameter #E 0 basic additional VCID #1 basicadditional (RRC set #1) DMRS pattern DMRS pattern DMRS pattern DMRSpattern overhead #1 overhead #1 position #1 position #1 1 basicadditional VCID #2 basic additional (RRC set #2) DMRS pattern DMRSpattern DMRS pattern DMRS pattern overhead #2 overhead #2 position #2position #2 2 basic additional VCID #3 basic additional (RRC set #3)DMRS pattern DMRS pattern DMRS pattern DMRS pattern overhead #3 overhead#3 position #3 position #3 3 basic additional VCID #4 basic additional(RRC set #4) DMRS pattern DMRS pattern DMRS pattern DMRS patternoverhead #4 overhead #4 position #4 position #4

In the example of Table 29, basic DMRS pattern overhead #1, #2, #3, and#4 may be respectively set via RRC signaling as described in the methodof signaling i) basic pattern overhead. The basic DMRS pattern overhead#1, #2, #3, and #4 may be set as different values, or some or all of thebasic DMRS pattern overhead #1, #2, #3, and #4 may be set as the samevalue.

As described in the method of signaling ii) additional pattern overhead,additional DMRS pattern overhead #1, #2, #3, and #4 may be respectivelyset via RRC signaling. The additional DMRS pattern overhead #1, #2, #3,and #4 may be set as different values, or some or all of the additionalDMRS pattern overhead #1, #2, #3, and #4 may be set as the same value.

As described in the method of signaling iii) an RE position (i.e., asymbol position and/or a subcarrier position) in a slot of a basicpattern, each of the basic DMRS pattern positions #1, #2, #3, and #4 maybe set via RRC signaling. The basic DMRS pattern positions #1, #2, #3,and #4 may be set as different values, or some or all of the basic DMRSpattern positions #1, #2, #3, and #4 may be set as the same value.

As described in the method of signaling iv) an RE position in a slot ofan additional pattern (i.e., a symbol position and/or a subcarrierposition), each of the additional DMRS pattern positions #1, #2, #3, and#4 may be set via RRC signaling. The additional DMRS pattern positions#1, #2, #3, and #4 may be set as different values, or some or all of theadditional DMRS pattern positions #1, #2, #3, and #4 may be set as thesame value.

As described in the method of signaling v) virtual cell identification,VCIDs #1, #2, #3, and #4 may be respectively set via RRC signaling. TheVCIDs #1, #2, #3, and #4 may be set as different values, or some or allof the VCIDs #1, #2, #3, and #4 may be set as the same value.

Embodiment 4

The present embodiment describes a method of setting signaling setcandidates including factors: i) basic pattern overhead (includinginformation indicating the existence of a basic pattern); ii) additionalpattern overhead (including information indicating the existence of anadditional pattern); iii) an RE position (i.e., a symbol position and/ora subcarrier position) in a slot of the basic pattern; and iv) an REposition (i.e., a symbol position and/or a subcarrier position) in aslot of the additional pattern. One of the candidates may be dynamicallyindicated using 1-bit information or 2-bit information included in DCI.

Table 30 provided below shows an example of dynamically indicating DMRSpattern configuration information using 1-bit information included inDCI.

TABLE 30 RRC RRC RRC RRC DCI bit value parameter #A parameter #Bparameter #C parameter #D 0 basic additional basic additional (RRC setDMRS pattern DMRS pattern DMRS pattern DMRS pattern candidate #1)overhead #1 overhead #1 position #1 position #1 1 basic additional basicadditional (RRC set DMRS pattern DMRS pattern DMRS pattern DMRS patterncandidate #2) overhead #2 overhead #2 position #2 position #2

In the example of Table 30, basic DMRS pattern overhead #1 and basicDMRS pattern overhead #2 may be respectively set via RRC signaling asdescribed in the method of signaling i) basic pattern overhead. Thebasic DMRS pattern overhead #1 and the basic DMRS pattern overhead #2may be set as the same value or different values.

As described in the method of signaling ii) additional pattern overhead,additional DMRS pattern overhead #1 and additional DMRS pattern overhead#2 may be respectively set via RRC signaling. The additional DMRSpattern overhead #1 and the additional DMRS pattern overhead #2 may beset as the same value or different values.

As described in the method of signaling iii) an RE position (i.e., asymbol position and/or a subcarrier position) in a slot of a basicpattern, each of the basic DMRS pattern position #1 and the basic DMRSpattern position #2 may be respectively set via RRC signaling. The basicDMRS pattern position #1 and the basic DMRS pattern position #2 may beset as the same value or different values.

As described in the method of signaling iv) an RE position (i.e., asymbol position and/or a subcarrier position) in a slot of an additionalpattern, each of the additional DMRS pattern position #1 and theadditional DMRS pattern position #2 may be respectively set via RRCsignaling. The additional DMRS pattern position #1 and the additionalDMRS pattern position #2 may be set as the same value or differentvalues.

Table 31 provided below shows an example of dynamically indicating DMRSpattern configuration information using 2-bit information included inDCI.

TABLE 31 RRC RRC RRC RRC DCI bit value parameter #A parameter #Bparameter #C parameter #D 0 basic additional basic additional (RRC set#1) DMRS pattern DMRS pattern DMRS pattern DMRS pattern overhead #1overhead #1 position #1 position #1 1 basic additional basic additional(RRC set #2) DMRS pattern DMRS pattern DMRS pattern DMRS patternoverhead #2 overhead #2 position #2 position #2 2 basic additional basicadditional (RRC set #3) DMRS pattern DMRS pattern DMRS pattern DMRSpattern overhead #3 overhead #3 position #3 position #3 3 basicadditional basic additional (RRC set #4) DMRS pattern DMRS pattern DMRSpattern DMRS pattern overhead #4 overhead #4 position #4 position #4

In the example of Table 31, basic DMRS pattern overhead #1, #2, #3, and#4 may be respectively set via RRC signaling as described in the methodof signaling i) basic pattern overhead. The basic DMRS pattern overhead#1, #2, #3, and #4 may be set as different values, or some or all of thebasic DMRS pattern overhead #1, #2, #3, and #4 may be set as the samevalue.

As described in the method of signaling ii) additional pattern overhead,additional DMRS pattern overhead #1, #2, #3, and #4 may be respectivelyset via RRC signaling. The additional DMRS pattern overhead #1, #2, #3,and #4 may be set as different values, or some or all of the additionalDMRS pattern overhead #1, #2, #3, and #4 may be set as the same value.

As described in the method of signaling iii) an RE position (i.e., asymbol position and/or a subcarrier position) in a slot of a basicpattern, each of the basic DMRS pattern positions #1, #2, #3, and #4 maybe set via RRC signaling. The basic DMRS pattern positions #1, #2, #3,and #4 may be set as different values, or some or all of the basic DMRSpattern positions #1, #2, #3, and #4 may be set as the same value.

As described in the method of signaling iv) an RE position (i.e., asymbol position and/or a subcarrier position) in a slot of an additionalpattern, each of the additional DMRS pattern positions #1, #2, #3, and#4 may be set via RRC signaling. The additional DMRS pattern positions#1, #2, #3, and #4 may be set as different values, or some or all of theadditional DMRS pattern positions #1, #2, #3, and #4 may be set as thesame value.

v) virtual cell identification which is not included in a higher layersignaling set candidate may be set separately or independently via DCIor RRC signaling.

FIG. 11 is a diagram illustrating a method of signaling DMRS patternconfiguration information according to the present disclosure.

In operation S1110, a base station may determine signaling setcandidates for DMRS pattern configuration to be allocated to a terminal.One signaling set candidate may include configuration informationassociated with a combination of two or more factors from among basicpattern overhead (information indicating the existence of a basicpattern), additional pattern overhead (information indicating theexistence of an additional pattern), an RE position in a slot of thebasic pattern (i.e., a symbol position and/or subcarrier position), anRE position in a slot of the additional pattern (i.e., a symbol positionand/or subcarrier position), or virtual cell identification.

In operation S1120, the base station may inform the terminal of DMRSpattern configuration signaling set candidates via higher layersignaling (e.g., RRC signaling).

In operation S1130, the base station may determine one of the DMRSpattern configuration signaling set candidates, which is to be actuallyallocated to the terminal.

In operation S1140, the base station may inform the terminal ofinformation indicating the DMRS pattern configuration signaling set(i.e., one determined in operation S1130 from among the candidates) viadynamic signaling (e.g., DCI).

In operation S1150, the base station may map a DMRS onto a physicalresource according to a DMRS pattern corresponding to the indicatedsignaling set, and may transmit the same to the terminal. In thisinstance, the base station may also transmit a physical channel togetherin a slot in which the DMRS is transmitted.

In operation S1160, the terminal may demodulate a signal received viathe physical channel using channel information estimated based on theDMRS received from the base station.

In the example of FIG. 11, the factor that is not included in the DMRSpattern configuration signaling set candidates may be separately orindependently set for the terminal via RRC signaling or DCI.

FIG. 12 is a diagram illustrating the configurations of a base stationdevice and a terminal device according to the present disclosure.

The base station device 1200 may include a processor 1210, an antennaunit 1220, a transceiver 1230, and a memory 1240.

The processor 1210 may perform signal processing associated with abaseband, and may include an higher layer processing unit 1211 and aphysical layer processing unit 1215. The higher layer processing unit1211 may process operation of a Medium Access Control (MAC) layer, aRadio Resource Control (RRC), or a higher layer. The physical layerprocessing unit 1215 may process operation of a physical (PHY) layer(e.g., uplink reception signal processing and downlink transmissionsignal processing). The processor 1210 may control the overall operationof the base station device 1200, in addition to performingbaseband-related signal processing.

The antenna unit 1220 may include one or more physical antennas, and maysupport Multiple Input Multiple Output (MIMO) transmission and receptionwhen a plurality of antennas is included. The transceiver 1230 mayinclude an radio frequency (RF) transmitter and an RF receiver. Thememory 1240 may store processed information of the processor 1210,software associated with the operations of the base station device 1200,an operating system, applications, or the like, and may include elementssuch as a buffer or the like.

The processor 1210 of the base station device 1200 may be configured toimplement the operations of the base station described in theembodiments of the present disclosure.

For example, the higher layer processing unit 1211 of the processor 1210of the base station device 1200 may include a DMRS configurationgenerating unit 1212.

The DMRS pattern configuration information generating unit 1212 maydetermine DMRS configuration information signaling set candidates (e.g.,combinations of two or more factors from among basic pattern overhead(information indicating the existence of a basic pattern), additionalpattern overhead (information indicating the existence of an additionalpattern), an RE position (i.e., a symbol position and/or a subcarrierposition) in a slot of the basic pattern, an RE position (i.e., a symbolposition and/or a subcarrier position) in a slot of the additionalpattern, and virtual cell identification), for a DMRS transmitted inorder to demodulate a physical channel to be transmitted to a terminal,and may indicate the signaling set candidates to the terminal.

The physical layer processing unit 1215 of the processor 1210 of thebase station device 1200 may include a DMRS pattern configurationinformation transmitting unit 1216, a DMRS transmitting unit 1217, and aphysical channel transmitting unit 1218.

The DMRS pattern configuration information transmitting unit 1216 mayconfigure downlink control information (DCI) including DMRSconfiguration that is allocated to the terminal, and may transmit thesame via the transceiver 1230.

For example, the DMRS pattern configuration information transmittingunit 1216 may transmit DCI to the terminal, the DCI includinginformation indicating one of the DMRS pattern configuration informationsignaling set candidates generated by the DMRS pattern configurationinformation generating unit 1212 of the higher layer processing unit1210.

The DMRS transmitting unit 1217 may map a DMRS onto a physical resourcebased on the DMRS configuration allocated to the terminal, and maytransmit the same via the transceiver 1230.

The physical channel transmitting unit 1217 may map a physical channel(e.g., a downlink data channel) onto the physical resource, togetherwith the DMRS transmitted to the terminal, and may transmit the same viathe transceiver 1230.

The terminal device 1250 may include a processor 1260, an antenna unit1270, a transceiver 1280, and a memory 1290.

The processor 1260 may perform signal processing associated with abaseband, and may include a higher layer processing unit 1261 and aphysical layer processing unit 1265. The higher layer processing unit1261 may process operation of a MAC layer, an RRC layer, or a higherlayer. The physical layer processing unit 1265 may process operation ofa PHY layer (e.g., downlink reception signal processing and uplinktransmission signal processing). The processor 1260 may control theoverall operation of the terminal device 1250, in addition to performingbaseband-related signal processing.

The antenna unit 1270 may include one or more physical antennas, and maysupport MIMO transmission and reception when a plurality of antennas isincluded. The transceiver 1280 may include an RF transmitter and an RFreceiver. The memory 1290 may store processed information of theprocessor 1260, software associated with the operations of the terminaldevice 1250, an operating system, applications, or the like, and mayinclude elements such as a buffer or the like.

The processor 1260 of the terminal device 1250 may be configured toimplement the operations of the terminal described in the embodiments ofthe present disclosure.

The higher layer processing unit 1261 of the processor 1260 of theterminal device 1250 may include a DMRS pattern configurationinformation determining unit 1262.

The DMRS pattern configuration information determining unit 1262 maydetermine DMRS configuration information signaling set candidates (e.g.,combinations of two or more factors from among basic pattern overhead(information indicating the existence of a basic pattern), additionalpattern overhead (information indicating the existence of an additionalpattern), an RE position (i.e., a symbol position and/or a subcarrierposition) in a slot of the basic pattern, an RE position (i.e., a symbolposition and/or a subcarrier position) in a slot of the additionalpattern, and virtual cell identification) based on higher layersignaling provided from the base station.

The physical layer processing unit 1265 of the processor 1260 of theterminal device 1250 may include a DMRS pattern configurationinformation receiving unit 1266, a DMRS receiving unit 1267, and aphysical channel receiving unit 1268.

The DMRS pattern configuration information receiving unit 1266 mayreceive DMRS pattern configuration information provided via DCI from thebase station, via the transceiver 1280.

For example, the DMRS pattern configuration information receiving unit1266 may receive DCI including information indicating one of the DMRSpattern configuration information signaling set candidates determined bythe DMRS pattern configuration information determining unit 1262 of thehigher layer processing unit 1261.

The DMRS receiving unit 1267 may receive a DMRS via the transceiver1280, based on DMRS configuration identified via the DMRS configurationinformation receiving unit 1266.

The physical channel receiving unit 1268 may receive a physical channeltransmitted together with the DMRS, via the transceiver 1280.

The physical layer processing unit 1265 may transfer the received DMRSand physical channel to the higher layer processing unit 1261, and mayattempt to demodulate the physical channel based on channel informationestimated using the DMRS.

The descriptions provided in the embodiments of the present disclosurecan be equally applied to the operations of the base station device 1200and the terminal device 1250, and overlapping descriptions have beenomitted. An example method of transmitting a reference signal may beperformed by a base station (e.g., an eNodeB of an NR system) in adownlink or a UE (e.g., a UE of an NR system) in an uplink or asidelink. For example, a method may comprise determining a first set ofantenna ports for a demodulation reference signal (DM-RS) transmission;determining, based on the first set, a frequency index associated withfour adjacent resource elements, wherein the four adjacent resourceelements correspond to two adjacent symbols in a time axis and to twoadjacent subcarriers in a frequency axis; generating, based on a firstorthogonal cover code and a second orthogonal cover code, a DM-RSassociated with the first set of antenna ports; and transmitting, via amapping to the four adjacent resource elements, the DM-RS associatedwith the first set of antenna ports. The DM-RS may be a DM-RS for aphysical downlink shared channel (PDSCH), a DM-RS for a physical uplinkshared channel (PUSCH) or a DM-RS for a physical sidelink shared channel(PSSCH).

The first orthogonal cover code may be a length-2 orthogonal cover codeand may be associated with the two adjacent subcarriers, and the secondorthogonal cover code may be a length-2 orthogonal cover code and may beassociated with the two adjacent symbols. The method may furthercomprise determining three code division multiplexing (CDM) groups eachcomprising four different antenna ports, and a first CDM group, of thethree CDM groups, may comprise the first set of antenna ports.

The method may further comprise determining a second set of antennaports for a DM-RS transmission; determining, based on the second set, afrequency index associated with additional four adjacent resourceelements, wherein the additional four adjacent resource elementscorrespond to the two adjacent symbols in the time axis and toadditional two adjacent subcarriers in the frequency axis; generating,based on the first orthogonal cover code and the second orthogonal covercode, a DM-RS associated with the second set of antenna ports; andtransmitting, via a mapping to the additional four adjacent resourceelements, the DM-RS associated with the second set of antenna ports.

The four adjacent resource elements may comprise a first resourceelement having a symbol index x and a subcarrier index y, a secondresource element having a symbol index x and a subcarrier index (y+1), athird resource element having a symbol index (x+1) and a subcarrierindex y, and a fourth resource element having a symbol index (x+1) and asubcarrier index (y+1) where x and y are positive integers. A sequenceof four orthogonal cover code values for the first resource element, thesecond resource element, the third resource element, and the fourthresource element may be differently determined for each antenna port inthe first set (e.g., as shown in FIG. 10 and Table 21).

The method may further comprise determining a third set of antenna portsfor a DM-RS transmission; determining, based on the third set, afrequency index associated with second additional four adjacent resourceelements, wherein the second additional four adjacent resource elementscorrespond to the two adjacent symbols in the time axis and to secondadditional two adjacent subcarriers in the frequency axis; generating,based on the first orthogonal cover code and the second orthogonal covercode, a DM-RS associated with the third set of antenna ports; andtransmitting, via a mapping to the second additional four adjacentresource elements, the DM-RS associated with the third set of antennaports.

The method may further comprise determining to transmit DM-RS viaadditional two adjacent symbols; determining, based on the first set,the frequency index associated with additional four adjacent resourceelements, wherein the additional four adjacent resource elementscorrespond to the additional two adjacent symbols in the time axis andto the two adjacent subcarriers in the frequency axis; and transmitting,via a mapping to the additional four adjacent resource elements, a DM-RSassociated with the first set of antenna ports. At least one symbol mayexist between the two adjacent symbols and the additional two adjacentsymbols, and the two adjacent symbols and the additional two adjacentsymbols may be comprised in one slot.

If the DM-RS is a DM-RS for a PDSCH, the DM-RS associated with the firstset of antenna ports comprises a DM-RS for a PDSCH, and the transmittingthe DM-RS associated with the first set of antenna ports may comprisetransmitting, from a base station and to a user equipment, the DM-RSassociated with the first set of antenna ports. If the DM-RS is a DM-RSfor a PUSCH, the DM-RS associated with the first set of antenna portscomprises a DM-RS for a PUSCH, and the transmitting the DM-RS associatedwith the first set of antenna ports may comprise transmitting, from auser equipment and to a base station, the DM-RS associated with thefirst set of antenna ports. If the DM-RS is a DM-RS for a PSSCH, theDM-RS associated with the first set of antenna ports comprises a DM-RSfor a PSSCH, and the transmitting the DM-RS associated with the firstset of antenna ports may comprise transmitting, from a user equipmentand to another user equipment, the DM-RS associated with the first setof antenna ports.

An example method may comprise determining, by a base station, a type ofdemodulation reference signal (DM-RS) configuration; determining twoadjacent orthogonal frequency division multiplexing (OFDM) symbols formapping DM-RSs for at least three code division multiplexing (CDM)groups; determining a first set of antenna ports for a demodulationreference signal (DM-RS) transmission to a first user equipment (UE),wherein a first CDM group, among the at least three CDM groups,comprises the first set of antenna ports; determining, based on thefirst set, a frequency index associated with first four adjacentresource elements, wherein the first four adjacent resource elementscorrespond to the two adjacent OFDM symbols in a time axis and to firsttwo adjacent subcarriers in a frequency axis; and mapping, based on afirst orthogonal cover code and a second orthogonal cover code, a firstDM-RS to the first four adjacent resource elements, wherein the firstDM-RS is associated with the first set of antenna ports.

The method may further comprise determining a second set of antennaports for a DM-RS transmission to a second UE, wherein a second CDMgroup, among the at least three CDM groups, comprises the second set ofantenna ports; determining, based on the second set, a frequency indexassociated with second four adjacent resource elements, wherein thesecond four adjacent resource elements correspond to the two adjacentOFDM symbols in the time axis and to second two adjacent subcarriers inthe frequency axis; and mapping, based on the first orthogonal covercode and the second orthogonal cover code, a second DM-RS to the secondfour adjacent resource elements, wherein the second DM-RS is associatedwith the second set of antenna ports.

The method may further comprise determining a second set of antennaports for a DM-RS transmission to the first UE, wherein a second CDMgroup, among the at least three CDM groups, comprises the second set ofantenna ports; determining, based on the second set, a frequency indexassociated with second four adjacent resource elements, wherein thesecond four adjacent resource elements correspond to the two adjacentOFDM symbols in the time axis and to second two adjacent subcarriers inthe frequency axis; and mapping, based on the first orthogonal covercode and the second orthogonal cover code, a second DM-RS to the secondfour adjacent resource elements, wherein the second DM-RS is associatedwith the second set of antenna ports.

The first set of antenna ports may comprise one to four antenna portsnot comprised in the second CDM group or a third CDM group of the atleast three CDM groups, and the second set of antenna ports may compriseone to four antenna ports not comprised in the first CDM group or thethird CDM group.

Antenna ports in the second CDM group may be configured to be selectedfor a DM-RS transmission after selecting at least one antenna port, fromthe first CDM group, for a DM-RS transmission, and antenna ports in thethird CDM group may be configured to be selected for a DM-RStransmission after selecting at least one antenna port, from the secondCDM group, for a DM-RS transmission.

An example method may comprise receiving, by a user equipment (UE) andfrom a base station, a type of demodulation reference signal (DM-RS)configuration, a first set of antenna ports for a DM-RS transmissionfrom the UE, and information indicating a quantity of code divisionmultiplexing (CDM) groups scheduled for a DM-RS transmission;determining two adjacent symbols for mapping a DM-RS; determining, basedon the first set, a frequency index associated with first four adjacentresource elements, wherein the first four adjacent resource elementscorrespond to the two adjacent symbols in a time axis and to first twoadjacent subcarriers in a frequency axis; generating, based on a firstorthogonal cover code and a second orthogonal cover code, a DM-RSassociated with the first set of antenna ports; and transmitting, via amapping to the first four adjacent resource elements, the DM-RSassociated with the first set of antenna ports.

The method may further comprise determining, based on the informationindicating a quantity of CDM groups scheduled for a DM-RS transmission,whether to map a physical uplink shared channel (PUSCH) to second fouradjacent resource elements, wherein the second four adjacent resourceelements correspond to the two adjacent symbols in the time axis and tosecond two adjacent subcarriers in a frequency axis.

A first CDM group, among three CDM groups, may comprise the first set ofantenna ports, antenna ports in a second CDM group, among the three CDMgroups, may be configured to be selected for a DM-RS transmission afterselecting at least one antenna port, from the first CDM group, for aDM-RS transmission, and antenna ports in a third CDM group, among thethree CDM groups, may be configured to be selected for a DM-RStransmission after selecting at least one antenna port, from the secondCDM group, for a DM-RS transmission. The method may further comprisedetermining that the quantity of CDM groups scheduled for a DM-RStransmission corresponds to two or three. The determining whether to mapthe PUSCH to second four adjacent resource elements may comprisedetermining not to map the PUSCH to the second four adjacent resourceelements.

In order to solve a problem in that a wide bandwidth is not used in aconventional frequency range or in a carrier such as 700 MHz or 2 GHz, anew numerology for an NR system supporting a plurality of subcarrierspacings (SCS) may be determined by assuming a wireless communicationsystem operating in a frequency range or in a carrier such as 3 GHz orlower, 3 GHz-6 GHz, or 6 GHZ-52.6 GHz, but a range of the presentdisclosure is not limited thereto.

In the NR system, one radio frame may correspond to 10 ms on a temporalaxis, and one subframe may correspond to 1 ms on a temporal axis. Inaddition, one slot may correspond to fourteen or seven symbols on atemporal axis. Accordingly, a number of available slots and symbolsaccording to a subcarrier spacing (SCS) respectively in considerationwithin one radio frame corresponding to 10 ms is as Table 1 below. InTable 1, an SCS of 480 KHz may not be considered.

TABLE 32 Number of slots Number of slots within 10 ms within 10 ms(fourteen symbols (seven symbols in Number of symbols SCS in one slot)one slot) within 10 ms  15 KHz 10 20 140  30 Khz 20 40 280  60 KHz 40 80560 120 KHz 80 N/A 1120 240 KHz 160 N/A 2240 480 KHz 320 N/A 4480

In detail, hereinafter, various examples of the present disclosure for aDMRS layer, an antenna port, a sequence, and a multiplexing for the NRsystem will be described.

In an MU-MIMO, up to 12 layers being classified from each other may besupported for across all terminals. In other words, in the MU-MIMO, eachlayer used by each terminal may be one of DMRS antenna port numbers #1,#2, #3, #4, #5, #6, #7, #8, #9, #10, #11, and #12, which are differentfrom each other.

In addition, a maximum number N of available DMRS layers for eachterminal may be respectively defined for a case of an SU-MIMO and a caseof an MU-MIMO.

In case of an SU-MIMO, up to N=8 layers classified from each other maybe supported for one terminal.

In case of an MU-MIMO, up to N=2 (or N=3 or N=4) layers classified fromeach other may be supported for each terminal.

When a maximum number of available DMRS layers for each terminal is N,each layer may correspond to one of DMRS antenna port numbers #1, #2,#3, #4, #5, #6, #7, #8, #9, #10, #11, and #12, which is different fromeach other.

A DMRS for the NR system may be defined to be arranged up three DMRStypes within one slot.

As the three DMRS types, a front-loaded DMRS, a first additional DMRS(Additional DMRS #1), and a second additional DMRS (Additional DMRS #2)may be defined.

The front-loaded DMRS may be basically arranged in one OFDM symbol thatis positioned at a temporally front part within one slot or in twoconsecutive OFDM symbols within one slot. In addition, when a supportfor a channel temporally rapidly changing is required due to a fastmovement speed, at least one of Additional DMRS #1 and Additional DMRS#2 may be additionally arranged within one slot.

DMRS Pattern A

A DMRS pattern A is an example where a DMRS configuration type 1 isapplied. The DMRS configuration type 1 may be called an interleavedfrequency division multiple access (IFDMA) method or a comb method. Inother words, the DMRS configuration type 1 corresponds to a method inwhich one DMRS pattern is arranged in an alternate subcarrier in afrequency domain.

DMRS Pattern A-1

A DMRS pattern A-1 corresponds a case where one symbol is used, and mayclassify up to four DMRS antenna port.

FIG. 13 is a view showing an example of a DMRS pattern to which thepresent disclosure may be applied.

In the example of FIG. 13, in one symbol and twelve subcarriers(corresponding to one PRB in a frequency domain), a “Comb Pattern A” anda “Comb Pattern B” are represented. A DMRS pattern shown in FIG. 1 mayexpand, in a frequency axis, by being repeated to a plurality of PRBs bya bandwidth assigned for transmitting to a physical channel (forexample, physical downlink shared channel (PDSCH), physical uplinkshared channel (PUSCH), etc.) of each terminal. In addition, in atemporal axis, the DMRS pattern may be applied to each DMRSconfiguration (for example, front-loaded DMRS configuration, AdditionalDMRS #1 configuration, and Additional DMRS #2 configuration) within oneslot.

FIG. 13 shows examples of, for one symbol within one PRB, respectivelyassigning six REs for a Comb Pattern A and a Comb Pattern B in case of afull overhead, and respectively assigning three REs in case of a ½overhead that is when an overhead reduction is applied. However, it isnot limited thereto, and an overhead reduction of another frequency maybe used. For example, for each Comb Pattern, in one symbol within onePRB, two REs (in other words, applying a ⅓ overhead), four REs (in otherwords, applying a ⅔ overhead) may be assigned.

Relating to the example of FIG. 13, a DMRS antenna port configurationmay be defined as Table 2 or Table 3 below. In Tables 2 and 3 below, aComb pattern is the “Comb pattern A” or the “Comb pattern B” shown inFIG. 13. A cyclic shift (CS) is a cyclic delay value of a DMRS sequence.When a number of available values is X, a “CS value A” may have a valueof 0, and a “CS value B” may represent to have a value of X/2. Forexample, when X=12, the “CS value A” may have a value of 0, and the “CSvalue B” may have a value of 6. When X=2π, the “CS value A” may have avalue of 0, and the “CS value B” may have a value of π, but it is notlimited thereto.

DMRS Pattern A-1-1

A DMRS pattern A-1-1 preferentially classifies DMRS antenna ports intoComb patterns, and within a range to which the same Comb Pattern isapplied, the DMRS pattern A-1-1 corresponds to a method of classifyinginto CS values. Table 33 below shows an example thereof.

TABLE 33 Comb pattern CS (Cyclic Shift) DMRS antenna port #1 Combpattern A CS value A DMRS antenna port #2 Comb pattern B CS value A DMRSantenna port #3 Comb pattern A CS value B DMRS antenna port #4 Combpattern B CS value B

DMRS Pattern A-1-2

A DMRS pattern A-1-2 preferentially classifies DMRS antenna ports intoCS values, and within a range to which the same CS value is applied, theDMRS pattern A-1-2 corresponds to a method of classifying into CombPatterns. Table 34 below shows an example thereof.

TABLE 34 Comb pattern CS (Cyclic Shift) DMRS antenna port #1 Combpattern A CS value A DMRS antenna port #2 Comb pattern A CS value B DMRSantenna port #3 Comb pattern B CS value A DMRS antenna port #4 Combpattern B CS value B

DMRS Pattern A-2

A DMRS pattern A-2 corresponds to a case where two symbols are used, andthe DMRS pattern A-2 may classify up to eight DMRS antenna ports.

FIG. 14 is a view showing an additional example of a DMRS pattern towhich the present disclosure may be applied.

In the example of FIG. 14, in two symbols and twelve subcarriers(corresponding to one PRB in a frequency domain), a “Comb Pattern A” and“Comb Pattern B” are represented. A DMRS pattern shown in FIG. 14 mayexpand, in a frequency axis, by being repeated to a plurality of PRBs bya bandwidth assigned for transmitting to a physical channel (forexample, PDSCH, PUSCH, etc.) In addition, in a temporal axis, the DMRSpattern may be applied to each DMRS configuration (for example,front-loaded DMRS configuration, Additional DMRS #1 configuration, andAdditional DMRS #2 configuration) within one slot.

FIG. 14 shows examples of, for one symbol within one PRB, for therespectively Comb Pattern A and the Comb Pattern B, assigning six REs incase of a full overhead, and assigning three REs in case of a ½ overheadthat is when an overhead reduction is applied. However, it is notlimited thereto, and an overhead reduction of another frequency may beused. For example, for each Comb Pattern, in one symbol within one PRB,two REs (in other words, applying a ⅓ overhead), four REs (in otherwords, applying a ⅔ overhead) may be assigned.

In other words, for respectively two symbols within one PRB, for theComb Pattern A and the Comb Pattern B, twelve REs may be assigned incase of a full overhead, six REs may be assigned in case of a ½ overheadthat is when a overhead reduction is applied, four REs may be assignedwhen a ⅓ overhead is applied, and eight REs may be assigned when a ⅔overhead is applied.

Relating to the example of FIG. 14, a DMRS antenna port configurationmay be defined as Tables following. In Tables, a Comb pattern is the“Comb pattern A” or the “Comb pattern B” shown in FIG. 14. A cyclicshift (CS) is a cyclic delay value of a DMRS sequence. When a number ofavailable values is X, a “CS value A” may have a value of 0, and a “CSvalue B” may represent to have a value of X/2. For example, when X=12,the “CS value A” may have a value of 0, and the “CS value B” may have avalue of 6. When X=2π, the “CS value A” may have a value of 0, and the“CS value B” may be a value of π, but it is not limited thereto.

In addition, a time domain-orthogonal cover code (TD-OCC) may be appliedto two REs that are adjacent in a temporal axis on the same subcarrierwithin each Comb pattern. In other words, a TD-OCC value of [+1, +1] or[+1, −1] may be applied to [RE with a temporal axial precedence on thesame subcarrier, RE following in a temporal axis on the samesubcarrier]. Accordingly, when generating a DMRS sequence, +1 or −1 ismultiplied by a sequence value of a DMRS sequence mapped to acorresponding RE.

DMRS Pattern A-2-1

A DMRS pattern A-2-1 preferentially classifies DMRS antenna ports intoComb patterns, and within a range to which the same Comb Pattern isapplied, the DMRS pattern A-2-1 classifies DMRS antenna ports into CSvalues. In addition, within a range to which the same Comb pattern andthe same CS value are applied, the DMRS pattern A-2-1 corresponds to amethod of classifying the DMRS antenna ports into TD-OCC values. Table35 below shows an example thereof.

TABLE 35 Comb pattern CS (Cyclic Shift) TD-OCC DMRS antenna port #1 Combpattern A CS value A [+1, +1] DMRS antenna port #2 Comb pattern B CSvalue A [+1, +1] DMRS antenna port #3 Comb pattern A CS value B [+1, +1]DMRS antenna port #4 Comb pattern B CS value B [+1, +1] DMRS antennaport #5 Comb pattern A CS value A [+1, −1] DMRS antenna port #6 Combpattern B CS value A [+1, −1] DMRS antenna port #7 Comb pattern A CSvalue B [+1, −1] DMRS antenna port #8 Comb pattern B CS value B [+1, −1]

DMRS Pattern A-2-2

A DMRS pattern A-2-2 preferentially classifies DMRS antenna ports intoComb patterns, and within a range to which the same Comb Pattern isapplied, the DMRS pattern A-2-2 classifies the DMRS antenna ports intoTD-OCC values. In addition, within a range to which the same Combpattern and the same TD-OCC value are applied, the DMRS pattern A-2-2corresponds to a method of classifying the DMRS antenna ports into CSvalues. Table 36 below shows an example thereof.

TABLE 36 Comb pattern CS (Cyclic Shift) TD-OCC DMRS antenna port #1 Combpattern A CS value A [+1, +1] DMRS antenna port #2 Comb pattern B CSvalue A [+1, +1] DMRS antenna port #3 Comb pattern A CS value A [+1, −1]DMRS antenna port #4 Comb pattern B CS value A [+1, −1] DMRS antennaport #5 Comb pattern A CS value B [+1, +1] DMRS antenna port #6 Combpattern B CS value B [+1, +1] DMRS antenna port #7 Comb pattern A CSvalue B [+1, −1] DMRS antenna port #8 Comb pattern B CS value B [+1, −1]

DMRS Pattern A-2-3

A DMRS pattern A-2-3 preferentially classifies DMRS antenna ports intoCS values, and within a range to which the same CS value is applied, theDMRS pattern A-2-3 classifies the DMRS antenna ports into Comb patterns.In addition, within a range to which the same CS value and the same Combpattern are applied, the DMRS pattern A-2-3 corresponds to a method ofclassifying the DMRS antenna ports into TD-OCC values. Table 37 belowshows an example thereof.

TABLE 37 Comb pattern CS (Cyclic Shift) TD-OCC DMRS antenna port #1 Combpattern A CS value A [+1, +1] DMRS antenna port #2 Comb pattern A CSvalue B [+1, +1] DMRS antenna port #3 Comb pattern B CS value A [+1, +1]DMRS antenna port #4 Comb pattern B CS value B [+1, +1] DMRS antennaport #5 Comb pattern A CS value A [+1, −1] DMRS antenna port #6 Combpattern A CS value B [+1, −1] DMRS antenna port #7 Comb pattern B CSvalue A [+1, −1] DMRS antenna port #8 Comb pattern B CS value B [+1, −1]

DMRS Pattern A-2-4

A DMRS pattern A-2-4 preferentially classifies DMRS antenna ports intoCS values, and within a range to which the same CS value is applied, theDMRS pattern A-2-4 classifies the DMRS antenna ports into TD-OCC values.In addition, within a range to which the same CS value and the sameTD-OCC value are applied, the DMRS pattern A-2-4 corresponds to a methodof classifying the DMRS antenna ports into Comb patterns. Table 38 belowshows an example thereof.

TABLE 38 CS (Cyclic Comb pattern Shift) TD-OCC DMRS antenna port #1 Combpattern A CS value A [+1, +1] DMRS antenna port #2 Comb pattern A CSvalue B [+1, +1] DMRS antenna port #3 Comb pattern A CS value A [+1, −1]DMRS antenna port #4 Comb pattern A CS value B [+1, −1] DMRS antennaport #5 Comb pattern B CS value A [+1, +1] DMRS antenna port #6 Combpattern B CS value B [+1, +1] DMRS antenna port #7 Comb pattern B CSvalue A [+1, −1] DMRS antenna port #8 Comb pattern B CS value B [+1, −1]

DMRS Pattern A-2-5

A DMRS pattern A-2-5 preferentially classifies DMRS antenna ports intoTD-OCC values, and within a range to which the same TD-OCC value isapplied, the DMRS pattern A-2-5 classifies the DMRS antenna ports intoCS values. In addition, within a range to which the same TD-OCC valueand the same CS value are applied, the DMRS pattern A-2-5 corresponds toa method of classifying the DMRS antenna ports into Comb patterns. Table39 below shows an example thereof.

TABLE 39 CS (Cyclic Comb pattern Shift) TD-OCC DMRS antenna port #1 Combpattern A CS value A [+1, +1] DMRS antenna port #2 Comb pattern A CSvalue A [+1, −1] DMRS antenna port #3 Comb pattern A CS value B [+1, +1]DMRS antenna port #4 Comb pattern A CS value B [+1, −1] DMRS antennaport #5 Comb pattern B CS value A [+1, +1] DMRS antenna port #6 Combpattern B CS value A [+1, −1] DMRS antenna port #7 Comb pattern B CSvalue B [+1, +1] DMRS antenna port #8 Comb pattern B CS value B [+1, −1]

DMRS Pattern A-2-6

A DMRS pattern A-2-6 preferentially classifies DMRS antenna ports intoTD-OCC values, and within a range to which the same TD-OCC value isapplied, the DMRS pattern A-2-6 classifies the DMRS antenna ports intoComb patterns. In addition, within a range to which the same TD-OCCvalue and the same Comb pattern are applied, the DMRS pattern A-2-6corresponds to a method of classifying the DMRS antenna ports into CSvalues. Table 40 below shows an example thereof.

TABLE 40 Comb pattern CS (Cyclic Shift) TD-OCC DMRS antenna port #1 Combpattern A CS value A [+1, +1] DMRS antenna port #2 Comb pattern A CSvalue A [+1, −1] DMRS antenna port #3 Comb pattern B CS value A [+1, +1]DMRS antenna port #4 Comb pattern B CS value A [+1, −1] DMRS antennaport #5 Comb pattern A CS value B [+1, +1] DMRS antenna port #6 Combpattern A CS value B [+1, −1] DMRS antenna port #7 Comb pattern B CSvalue B [+1, +1] DMRS antenna port #8 Comb pattern B CS value B [+1, −1]

DMRS Pattern B

A DMRS pattern B is an example where a DMRS configuration type 2 isapplied. The DMRS configuration type 2 may be called a code divisionmultiplexing (CDM) method. In other words, according to the DMRSconfiguration type 2, in CDM groups different from each other, DMRSantenna ports may be classified by being arranged in temporal-frequencyresources different from each other. In addition, within the same CDMgroup, the DMRS antenna ports may be classified by other code resourcesdifferent from each other (for example, OCC).

DMRS Pattern B-1

A DMRS pattern B-1 corresponds to a case where one symbol is used, andthe DMRS pattern B-1 may classify up to six DMRS antenna ports.

FIG. 15 is a view showing an additional example of a DMRS pattern towhich the present disclosure may be applied.

In the example of FIG. 15, in one symbol and twelve subcarriers(corresponding to one PRB in a frequency domain), a “CDM group A”, a“CDM group B”, and a “CDM group C” are represented. A DMRS pattern shownin FIG. 15 may expand, in a frequency axis, by being repeated to aplurality of PRBs as much as a bandwidth assigned for transmitting to aphysical channel (for example PDSCH, PUSCH, etc.). In addition, in atemporal axis, the DMRS pattern may be applied to each DMRSconfiguration (for example, front-loaded DMRS configuration, AdditionalDMRS #1 configuration, and Additional DMRS #2 configuration) within oneslot.

FIG. 15 shows examples of, for one symbol within one PRB, assigning fourREs to each CDM group in case of a full overhead, and assigning two REsin case of a ½ overhead that occurs when a overhead reduction isapplied.

Relating to the examples of FIG. 15, a DMRS antenna port configurationmay be defined as Table 41 or Table 42 below. In Tables, a CDM group isthe “CDM group A”, the “CDM group B”, or the “CDM group C” shown in FIG.15.

In addition, a frequency domain-orthogonal cover code (FD-OCC) may beapplied to two REs that are adjacent in a frequency axis on the samesymbol within each CDM group. In other words, a FD-OCC value of [+1, +1]or [+1, −1] may be applied to [RE with a frequency axial precedence onthe same symbol, RE following in a frequency axis on the same symbol].Accordingly, when generating a DMRS sequence, +1 or −1 is multiplied bya sequence value of a DMRS sequence mapped to a corresponding RE.

DMRS Pattern B-1-1

A DMRS pattern B-1-1 preferentially classifies DMRS antenna ports intoCDM groups, and within a range to which the same CDM group is applied,the DMRS pattern B-1-1 corresponds to a method of classifying the DMRSantenna ports into FD-OCC values. Table 41 below shows an examplethereof

TABLE 41 CDM group FD-OCC DMRS antenna port #1 CDM group A [+1, +1] DMRSantenna port #2 CDM group B [+1, +1] DMRS antenna port #3 CDM group C[+1, +1] DMRS antenna port #4 CDM group A [+1, −1] DMRS antenna port #5CDM group B [+1, −1] DMRS antenna port #6 CDM group C [+1, −1]

DMRS Pattern B-1-2

A DMRS pattern B-1-2 preferentially classifies DMRS antenna ports intoFD-OCC values, and within a range to which the same FD-OCC value isapplied, the DMRS pattern B-1-2 corresponds to a method of classifyingthe DMRS antenna ports into CDM groups. Table 11 below shows an examplethereof.

TABLE 42 CDM group FD-OCC DMRS antenna port #1 CDM group A [+1, +1] DMRSantenna port #2 CDM group A [+1, −1] DMRS antenna port #3 CDM group B[+1, +1] DMRS antenna port #4 CDM group B [+1, −1] DMRS antenna port #5CDM group C [+1, +1] DMRS antenna port #6 CDM group C [+1, −1]

DMRS Pattern B-2

A DMRS pattern B-2 corresponds to a case where two symbols are used, andthe DMRS pattern B-2 may classify up to twelve DMRS antenna ports.

FIG. 16 is a view showing an additional example of a DMRS pattern towhich the present disclosure may be applied.

In the example of FIG. 16, in two symbols and twelve subcarriers(corresponding to one PRB in a frequency domain), a “CDM group A”, a“CDM group B”, and a “CDM group C” are represented. A DMRS pattern shownin FIG. 16 may expand, to a frequency axis, by being repeated to aplurality of PRBs by a bandwidth assigned for transmitting a physicalchannel of each terminal (for example, PDSCH, PUSCH, etc.). In addition,in a temporal axis, the DMRS pattern may be applied to each DMRSconfiguration (for example, front-loaded DMRS configuration, AdditionalDMRS #1 configuration, and Additional DMRS #2 configuration) within oneslot.

FIG. 16 shows examples of, for one symbol within one PRB, for each CDMgroup, assigning four REs in case of a full overhead, and assigning twoREs in case of a ½ overhead that occurs when an overhead reduction isapplied.

In other words, for two symbols within one PRB, for each CDM group,eight REs may be assigned in case of a full overhead, and four REs maybe assigned in case of a ½ overhead that occurs when an overheadreduction is applied.

Relating to the examples of FIG. 16, a DMRS antenna port configurationmay be defined as Tables 43 to 48 below. In Tables, a CDM group is the“CDM group A”, the “CDM group B”, and the “CDM group C” shown in FIG.16.

In addition, a frequency domain-orthogonal cover code (FD-OCC) may beapplied to two REs that are adjacent in a frequency axis on the samesymbol within each CDM group. In other words, a FD-OCC value of [+1, +1]or [+1, −1] may be respectively applied to [one of the two contiguousREs having a lower frequency index in the same symbol, the other one ofthe two contiguous REs having a higher frequency index in the samesymbol]. Accordingly, when generating a DMRS sequence, +1 or −1 ismultiplied by a sequence value of a DMRS sequence that is mapped to acorresponding RE.

In addition, a time domain-orthogonal cover code (TD-OCC) may be appliedto two contiguous REs along a time axis on the same subcarrier withineach CDM group. In other words, a TD-OCC value of [+1, +1] or [+1, −1]may be respectively applied to [one of the two contiguous REs having alower symbol index on the same subcarrier, the other one of the two REshaving a higher symbol index on the same subcarrier]. Accordingly, whengenerating a DMRS sequence, +1 or −1 is multiplied by a sequence valueof a DMRS sequence that is mapped to a corresponding RE.

DMRS Pattern B-2-1

A DMRS pattern B-2-1 preferentially classifies DMRS antenna ports intoCDM groups, and within a range to which the same CDM group is applied,the DMRS pattern B-2-1 classifies the DMRS antenna ports into FD-OCCvalues. In addition, within a range to which the same CDM group and thesame FD-OCC value are applied, the DMRS pattern B-2-1 corresponds to amethod of classifying the DMRS antenna ports into TD-OCC values. Table43 below shows an example thereof.

TABLE 43 CDM group FD-OCC TD-OCC DMRS antenna port #1 CDM group A [+1,+1] [+1, +1] DMRS antenna port #2 CDM group B [+1, +1] [+1, +1] DMRSantenna port #3 CDM group C [+1, +1] [+1, +1] DMRS antenna port #4 CDMgroup A [+1, −1] [+1, +1] DMRS antenna port #5 CDM group B [+1, −1] [+1,+1] DMRS antenna port #6 CDM group C [+1, −1] [+1, +1] DMRS antenna port#7 CDM group A [+1, +1] [+1, −1] DMRS antenna port #8 CDM group B [+1,+1] [+1, −1] DMRS antenna port #9 CDM group C [+1, +1] [+1, −1] DMRSantenna port #10 CDM group A [+1, −1] [+1, −1] DMRS antenna port #11 CDMgroup B [+1, −1] [+1, −1] DMRS antenna port #12 CDM group C [+1, −1][+1, −1]

DMRS Pattern B-2-2

A DMRS pattern B-2-2 preferentially classifies DMRS antenna ports intoCDM groups, and within a range to which the same CDM group is applied,the DMRS pattern B-2-2 classifies the DMRS antenna ports into TD-OCCvalues. In addition, within a range to which the same CDM group and thesame TD-OCC value are applied, the DMRS pattern B-2-2 corresponds to amethod of classifying the DMRS antenna ports into FD-OCC values. Table44 below shows an example thereof.

TABLE 44 CDM group FD-OCC TD-OCC DMRS antenna port #1 CDM group A [+1,+1] [+1, +1] DMRS antenna port #2 CDM group B [+1, +1] [+1, +1] DMRSantenna port #3 CDM group C [+1, +1] [+1, +1] DMRS antenna port #4 CDMgroup A [+1, +1] [+1, −1] DMRS antenna port #5 CDM group B [+1, +1] [+1,−1] DMRS antenna port #6 CDM group C [+1, +1] [+1, −1] DMRS antenna port#7 CDM group A [+1, −1] [+1, +1] DMRS antenna port #8 CDM group B [+1,−1] [+1, +1] DMRS antenna port #9 CDM group C [+1, −1] [+1, +1] DMRSantenna port #10 CDM group A [+1, −1] [+1, −1] DMRS antenna port #11 CDMgroup B [+1, −1] [+1, −1] DMRS antenna port #12 CDM group C [+1, −1][+1, −1]

DMRS Pattern B-2-3

A DMRS pattern B-2-3 may classify DMRS antenna ports into FD-OCC values,and within a range to which the same FD-OCC value is applied, the DMRSpattern B-2-3 may classify the DMRS antenna ports into CDM groups. Inaddition, within a range to which the same FD-OCC value and the same CDMgroup are applied, the DMRS pattern B-2-3 may correspond to a method ofclassifying the DMRS antenna ports into TD-OCC values. Table 45 belowshows an example thereof.

TABLE 45 CDM group FD-OCC TD-OCC DMRS antenna port #1 CDM group A [+1,+1] [+1, +1] DMRS antenna port #2 CDM group A [+1, −1] [+1, +1] DMRSantenna port #3 CDM group B [+1, +1] [+1, +1] DMRS antenna port #4 CDMgroup B [+1, −1] [+1, +1] DMRS antenna port #5 CDM group C [+1, +1] [+1,+1] DMRS antenna port #6 CDM group C [+1, −1] [+1, +1] DMRS antenna port#7 CDM group A [+1, +1] [+1, −1] DMRS antenna port #8 CDM group A [+1,−1] [+1, −1] DMRS antenna port #9 CDM group B [+1, +1] [+1, −1] DMRSantenna port #10 CDM group B [+1, −1] [+1, −1] DMRS antenna port #11 CDMgroup C [+1, +1] [+1, −1] DMRS antenna port #12 CDM group C [+1, −1][+1, −1]

DMRS Pattern B-2-4

A DMRS pattern B-2-4 preferentially classifies DMRS antenna ports intoFD-OCC values, and within a range to which the same FD-OCC value isapplied, the DMRS pattern B-2-4 classifies the DMRS antenna ports intoTD-OCC values. In addition, within a range to which the same FD-OCCvalue and the same TD-OCC value are applied, the DMRS pattern B-2-4corresponds to a method of classifying the DMRS antenna ports into CDMgroups.

Table 46 below shows an example thereof.

TABLE 46 CDM group FD-OCC TD-OCC DMRS antenna port #1 CDM group A [+1,+1] [+1, +1] DMRS antenna port #2 CDM group A [+1, −1] [+1, +1] DMRSantenna port #3 CDM group A [+1, +1] [+1, −1] DMRS antenna port #4 CDMgroup A [+1, −1] [+1, −1] DMRS antenna port #5 CDM group B [+1, +1] [+1,+1] DMRS antenna port #6 CDM group B [+1, −1] [+1, +1] DMRS antenna port#7 CDM group B [+1, +1] [+1, −1] DMRS antenna port #8 CDM group B [+1,−1] [+1, −1] DMRS antenna port #9 CDM group C [+1, +1] [+1, +1] DMRSantenna port #10 CDM group C [+1, −1] [+1, +1] DMRS antenna port #11 CDMgroup C [+1, +1] [+1, −1] DMRS antenna port #12 CDM group C [+1, −1][+1, −1]

DMRS Pattern B-2-5

A DMRS pattern B-2-5 preferentially classifies DMRS antenna ports intoTD-OCC values, and within a range to which the same TD-OCC value isapplied, the DMRS pattern B-2-5 classifies the DMRS antenna ports intoCDM groups. In addition, within a range to which the same TD-OCC valueand the same CDM group are applied, the DMRS pattern B-2-5 correspondsto a method of classifying the DMRS antenna ports into FD-OCC values.Table 47 below shows an example thereof.

TABLE 47 CDM group FD-OCC TD-OCC DMRS antenna port #1 CDM group A [+1,+1] [+1, +1] DMRS antenna port #2 CDM group A [+1, +1] [+1, −1] DMRSantenna port #3 CDM group B [+1, +1] [+1, +1] DMRS antenna port #4 CDMgroup B [+1, +1] [+1, −1] DMRS antenna port #5 CDM group C [+1, +1] [+1,+1] DMRS antenna port #6 CDM group C [+1, +1] [+1, −1] DMRS antenna port#7 CDM group A [+1, −1] [+1, +1] DMRS antenna port #8 CDM group A [+1,−1] [+1, −1] DMRS antenna port #9 CDM group B [+1, −1] [+1, +1] DMRSantenna port #10 CDM group B [+1, −1] [+1, −1] DMRS antenna port #11 CDMgroup C [+1, −1] [+1, +1] DMRS antenna port #12 CDM group C [+1, −1][+1, −1]

DMRS Pattern B-2-6

A DMRS pattern B-2-6 preferentially classifies DMRS antenna ports intoTD-OCC values, and within a range to which the same TD-OCC value isapplied, the DMRS pattern B-2-6 classifies the DMRS antenna ports intoFD-OCC values. In addition, within a range to which the same TD-OCCvalue and the same FD-OCC value are applied, the DMRS pattern B-2-6corresponds to a method of classifying the DMRS antenna ports into CDMgroups. Table 48 below shows an example thereof.

TABLE 48 CDM group FD-OCC TD-OCC DMRS antenna port #1 CDM group A [+1,+1] [+1, +1] DMRS antenna port #2 CDM group A [+1, +1] [+1, −1] DMRSantenna port #3 CDM group A [+1, −1] [+1, +1] DMRS antenna port #4 CDMgroup A [+1, −1] [+1, −1] DMRS antenna port #5 CDM group B [+1, +1] [+1,+1] DMRS antenna port #6 CDM group B [+1, +1] [+1, −1] DMRS antenna port#7 CDM group B [+1, −1] [+1, +1] DMRS antenna port #8 CDM group B [+1,−1] [+1, −1] DMRS antenna port #9 CDM group C [+1, +1] [+1, +1] DMRSantenna port #10 CDM group C [+1, +1] [+1, −1] DMRS antenna port #11 CDMgroup C [+1, −1] [+1, +1] DMRS antenna port #12 CDM group C [+1, −1][+1, −1]

FIG. 17 is a view showing an application example of a TD-OCC and aFD-OCC to which the present disclosure may be applied.

FIG. 17 shows detailed examples where a “TD-OCC”, a “FD-OCC” a “FD-OCCand a TD-OCC” are mapped to DMRS REs.

When a TD-OCC value is [+1, +1], for two REs corresponding to twoconsecutive symbols on the same subcarrier, a DMRS sequence value mappedto an RE of a low symbol index may be multiplied by +1, and a DMRSsequence value mapped to an RE of a next symbol index may be multipliedby +1.

When a TD-OCC value is [+1, −1], for two REs corresponding to twoconsecutive symbols on the same subcarrier, a DMRS sequence value mappedto an RE of a low symbol index may be multiplied by +1, and a DMRSsequence value mapped to an RE of a next symbol index may be multipliedby −1.

When a FD-OCC value is [+1, +1], for two REs corresponding to twoconsecutive subcarriers on the same symbol, a DMRS sequence value mappedto an RE of a low subcarrier index may be multiplied by +1, and a DMRSsequence value mapped to an RE of a next subcarrier index may bemultiplied by +1.

When a FD-OCC value is [+1, −1], for two REs corresponding to twoconsecutive subcarriers on the same symbol, a DMRS sequence value mappedto an RE of a low subcarrier index may be multiplied by +1, and a DMRSsequence value mapped to an RE of a next subcarrier index may bemultiplied by −1.

In Examples where both of TD-ODD and FD-OCC are applied, according tothe above method, for REs belonging to the same CDM group, an OCC valuemay be multiplied in a temporal axis and a frequency axis.

Hereinafter, a method of indicating a DMRS layer and an antenna port foran NR system according to the present disclosure, and an apparatusthereof will be described.

According to the present disclosure, in a DMRS used for demodulating adata channel in an NR system, when configuring a layer and an antennaport for transmitting a DMRS and indicating the same, the followingaspects may be considered.

-   -   Various types of a DMRS configuration: a DMRS configuration type        1 may correspond to an IFDMA (or Comb) method, and a DMRS        configuration type 2 may correspond to a CDM group method.    -   A number of DMRS symbols: one symbol or two symbol may be used        for transmitting a DMRS in each DMRS configuration type.    -   A number of available layers being classified from each other        for each terminal according to an MIMO method: up to eight        layers may be classified for one terminal in a SU-MIMO, and up        to two (or three or four) layers may be classified for each        terminal in an MU-MIMO.    -   Up to twelve layers may be classified for across all terminals        in an MU-MIMO.

A signaling method of configuring a layer and an antenna port fortransmitting a DMRS, and indicating the same, in order to classify intoa DMRS configuration type 1 and a DMRS configuration type 2, a highclass signaling method (for example, radio resource control (RRC)signaling) may be used.

For each DMRS configuration type, a number of layers, an antenna portnumber, and a number of symbols which are used for receiving a DMRS ortransmitting a DMRS for each terminal may be indicated by a specificsignaling field defined within a specific downlink control information(DCI) format.

When transmitting a downlink (DL) DMRS, a base station may determine aDMRS configuration type of a DMRS to be transmitted, and may transmit toa terminal the determined DMRS configuration type by using a RRCsignaling method. The base station may determine a number of layers, anantenna port number, and a number of symbols of the DMRS to betransmitted to a terminal based on the DMRS configuration type, and maytransmit the same to the terminal by using DCI. The base station maytransmit the DMRS to the terminal by mapping on a physical resourcebased on the DMRS configuration type, and information of the number oflayers, the antenna port number, and the number of symbols of the DMRS.

When receiving a downlink (DL) DMRS, the terminal may receive and checkthe DMRS configuration type and information of the DMRS which will betransmitted from the base station to the terminal by using a RRCsignaling method. The terminal may receive and check information of thenumber of layers, the antenna port number, and the number of symbolslayers of the DMRS which are determined based on the DMRS configurationtype of the DMRS which will be transmitted from the base station to theterminal by using DCI transmitted from the base station to the terminal.The terminal may generate a DMRS based on information of the DMRSconfiguration type, the number of layers, the antenna port number, andthe number of symbols, and estimate a downlink channel by comparing theDMRS received from the base station and the generated DMRS.

When receiving an uplink (UL) DMRS, the base station may determine aDMRS configuration type of a DMRS to be transmitted from the terminal tothe base station, and transmit the determined DMRS configuration type tothe terminal by using RRC signaling. The base station may determine anumber of layers, an antenna port number, and a number of symbols of theDMRS to be transmitted from the terminal to the base station based onthe DMRS configuration type, and transmit the same to the terminal byusing DCI. The base station may generate a DMRS based on the DMRSconfiguration type and the information of the number of layers, theantenna port number, and the number of symbols of the DMRS, and estimatean uplink channel by comparing the DMRS received from the terminal andthe generated DMRS.

When transmitting an uplink (UL) DMRS, the terminal may receive andcheck from the base station information of a DMRS configuration type ofa DMRS to be transmitted from the terminal to the base station by usingRRC signaling. The terminal may receive and check information of anumber of layers, an antenna port number, and a number of symbols of theDMRS determined based on the DMRS configuration type of the DMRS to betransmitted from the terminal to the base station by using DCI that istransmitted from the base station to the terminal. The terminal maytransmit the DMRS to the base station by mapping on a physical resourcebased on the DMRS configuration type and the information of the numberof layers, the antenna port number, and the number of symbols of theDMRS.

Embodiment 5

The present embodiment 5 relates to a method of configuring andindicating information of a number of layers, an antenna port number,and a number of symbols of a DMRS in case of a DMRS configuration type 1(in other words, a DMRS configuration type of an IFDMA (or Comb)method).

Hereinafter, in detailed examples, examples of a combination of a numberof layers, an antenna port number, and a number of symbols of a DMRS maybe represented in a single table form, and a value indicating a specificcombination among combinations configured as the above table form may betransmitted from the base station to the terminal by using DCI. In otherwords, in a DCI format, as examples below, a signaling field indicatinga number of layers, an antenna port number, and a number of symbols of aDMRS may be defined. When a corresponding signaling field has a specificvalue, a number of layers, an antenna port number, and a number ofsymbols of a DMRS which are mapped to the specific value may beindicated.

In addition, in detailed examples below, it is assumed that up to twocodewords are used in an NR system. In detail, it is assumed that, foreach terminal, when one to four layers are used, one codeword (forexample, codeword 0) is used, and when five to eight layers are used,two codewords (for example, codeword 0 and codeword 1) are used. Inaddition, it is assumed that one codeword may be mapped up to fourlayers, and one layer is mapped to one antenna port.

In addition, in detailed examples below, an order of bit valuesrepresented in Table is not limited thereto, the order may be out oforder, and content of a message may be identical. In other words, in thepresent disclosure, a mapping relation between the bit value and themessage is not restricted. In addition, detailed content of the messagemay be referenced with FIGS. 13 to 17, and the Tables 33 to 48.

Embodiment 5-1

The present embodiment 5-1 corresponds to a case where up to N=2 layersbeing classified from each other is supported for each terminal in anMU-MIMO.

Hereinafter, examples of a codeword and a DMRS antenna port numberaccording to a number of layers used for each terminal will bedescribed.

In case of one layer, codeword 0 is enabled, and codeword 1 is disabled.The enabled codeword 0 may be mapped to any one of DMRS antenna ports#1, #2, #3, #4, #5, #6, #7, and #8. Herein, when the codeword 0 ismapped to any one of the DMRS antenna ports #2, #3, #4, #5, #6, #7, and#8, it may correspond to a case where a corresponding terminal is in anMU-MIMO.

In case of two layers, codeword 0 is enabled, and codeword 1 isdisabled. The enabled codeword 0 may be mapped to any one of DMRSantenna ports #1 and #2, #3 and #4, #5 and #6, and #7 and #8. Herein,when the codeword 0 is mapped to any one of the DMRS antenna ports #3and #4, #5 and #6, and #7 and #8, it may correspond a case where acorresponding terminal is in an MU-MIMO.

In case of three layers, codeword 0 is enabled, and codeword 1 isdisabled. The enabled codeword 0 may be mapped to DMRS antenna ports #1to #3 (DMRS antenna ports #1˜#3).

In case of four layers, codeword 0 is enabled, and codeword 1 isdisabled. The enabled codeword 0 may be mapped to DMRS antenna ports #1to #4 (DMRS antenna ports #1˜#4).

In case of five layers, codeword 0 and codeword 1 are both enabled. Theenabled codeword 0 may be mapped to DMRS antenna ports #1 and #2, andthe enabled codeword 1 may be mapped to DMRS antenna ports #3 to #5(DMRS antenna ports #3˜#5).

In case of six layers, codeword 0 and codeword 1 are both enabled. Theenabled codeword 0 may be mapped to DMRS antenna ports #1 to #3 (DMRSantenna ports #1˜#3), and the enabled codeword 1 may be mapped to DMRSantenna ports #4 to #6 (DMRS antenna ports #4˜#6).

In case of seven layers, codeword 0 and codeword 1 are both enabled. Theenabled codeword 0 may be mapped to DMRS antenna ports #1 to #3 (DMRSantenna ports #1˜#3), and the enabled codeword 1 may be mapped to DMRSantenna ports #4 to #7 (DMRS antenna ports #4˜#7).

In case of eight layers, codeword 0 and codeword 1 are both enabled. Theenabled codeword 0 may be mapped to DMRS antenna ports #1 to #4 (DMRSantenna ports #1˜#4), and the enabled codeword 1 may be mapped to DMRSantenna ports #5 to #8 (DMRS antenna ports #5˜#8).

Table 49 below shows an example of indicating a number of symbols, anumber of layers, and an antenna port number for one codeword when onecodeword is enabled and the other codeword is disabled (in other words,codeword 0 is enabled, and codeword 1 is disabled). In other words, aspecific bit value in the table corresponds to a specific message, andthe specific message indicates a combination of a number of symbols, anumber of layers, and an antenna port number.

TABLE 49 Bit value Message 0 1 symbol, 1 layer, DMRS antenna ports #1 11 symbol, 1 layer, DMRS antenna ports #2 2 1 symbol, 1 layer, DMRSantenna ports #3 3 1 symbol, 1 layer, DMRS antenna ports #4 4 2 symbols,1 layer, DMRS antenna ports #1 5 2 symbols, 1 layer, DMRS antenna ports#2 6 2 symbols, 1 layer, DMRS antenna ports #3 7 2 symbols, 1 layer,DMRS antenna ports #4 8 2 symbols, 1 layer, DMRS antenna ports #5 9 2symbols, 1 layer, DMRS antenna ports #6 10 2 symbols, 1 layer, DMRSantenna ports #7 11 2 symbols, 1 layer, DMRS antenna ports #8 12 1symbol, 2 layers, DMRS antenna ports #1~#2 13 1 symbol, 2 layers, DMRSantenna ports #3~#4 14 2 symbols, 2 layers, DMRS antenna ports #1~#2 152 symbols, 2 layers, DMRS antenna ports #3~#4 16 2 symbols, 2 layers,DMRS antenna ports #5~#6 17 2 symbols, 2 layers, DMRS antenna ports#7~#8 18 1 symbol, 3 layers, DMRS antenna ports #1~#3 19 2 symbols, 3layers, DMRS antenna ports #1~#3 20 1 symbol, 4 layers, DMRS antennaports #1~#4 21 2 symbols, 4 layers, DMRS antenna ports #1~#4 22 Reserved. . . . . . 31 Reserved

Table 50 below shows an example of indicating a number of symbols, anumber of layers, and an antenna port number for two codewords when bothof two codewords are enabled (for example, when codeword 0 and codeword1 are both enabled). In other words, a specific bit value of the tablecorresponds to a specific message, and the specific message indicates acombination of a number of symbols, a number of layers, and antenna portnumber.

TABLE 50 Bit value Message 0 2 symbols, 5 layers, DMRS antenna ports#1~#5 1 2 symbols, 6 layers, DMRS antenna ports #1~#6 2 2 symbols, 7layers, DMRS antenna ports #1~#7 3 2 symbols, 8 layers, DMRS antennaports #1~#8 4 Reserved . . . . . . 1 Reserved

When one codeword of the Table 18 is enabled, in order to indicate anumber of symbols, a number of layers, and a DMRS antenna port number, asignaling field having a 5-bit size may be defined. The above signalingfield is sufficient for indicating a number of symbols, a number oflayers, and a DMRS antenna port number when two codewords of the Table50 are enabled. In addition, in order to configure in one signalingfield by combining the examples of the Table 18 and Table 19, a numberof cases to be indicated does not exceed 32, thus a signaling fieldhaving a 5-bit size may be identically used.

Table 51 below shows where a case when one codeword of the Table 49 isenabled and a case when two codewords of the Table 50 are enabled arecombined and represented in one table. The examples of the Table 18 andthe Table 50 may be used for a case where information of whether onecodeword is enabled or two codewords are used may be obtained inadvance. Table 51 below may be used for all cases where information of anumber of enabled codewords may be or may not be obtained (in otherwords, regardless of whether or not information of a number of enabledcodewords is obtained).

TABLE 51 Bit value Message 0 1 symbol, 1 layer, DMRS antenna ports #1,codeword 0 1 1 symbol, 1 layer, DMRS antenna ports #2, codeword 0 2 1symbol, 1 layer, DMRS antenna ports #3, codeword 0 3 1 symbol, 1 layer,DMRS antenna ports #4, codeword 0 4 2 symbols, 1 layer, DMRS antennaports #1, codeword 0 5 2 symbols, 1 layer, DMRS antenna ports #2,codeword 0 6 2 symbols, 1 layer, DMRS antenna ports #3, codeword 0 7 2symbols, 1 layer, DMRS antenna ports #4, codeword 0 8 2 symbols, 1layer, DMRS antenna ports #5, codeword 0 9 2 symbols, 1 layer, DMRSantenna ports #6, codeword 0 10 2 symbols, 1 layer, DMRS antenna ports#7, codeword 0 11 2 symbols, 1 layer, DMRS antenna ports #8, codeword 012 1 symbol, 2 layers, DMRS antenna ports #1~#2, codeword 0 13 1 symbol,2 layers, DMRS antenna ports #3~#4, codeword 0 14 2 symbols, 2 layers,DMRS antenna ports #1~#2, codeword 0 15 2 symbols, 2 layers, DMRSantenna ports #3~#4, codeword 0 16 2 symbols, 2 layers, DMRS antennaports #5~#6, codeword 0 17 2 symbols, 2 layers, DMRS antenna ports#7~#8, codeword 0 18 1 symbol, 3 layers, DMRS antenna ports #1~#3,codeword 0 19 2 symbols, 3 layers, DMRS antenna ports #1~#3, codeword 020 1 symbol, 4 layers, DMRS antenna ports #1~#4, codeword 0 21 2symbols, 4 layers, DMRS antenna ports #1~#4, codeword 0 22 2 symbols, 5layers, DMRS antenna ports #1~#5, codeword 0 & codeword 1 23 2 symbols,6 layers, DMRS antenna ports #1~#6, codeword 0 & codeword 1 24 2symbols, 7 layers, DMRS antenna ports #1~#7, codeword 0 & codeword 1 252 symbols, 8 layers, DMRS antenna ports #1~#8, codeword 0 & codeword 126 Reserved . . . . . . 31 Reserved

Embodiment 5-2

The present embodiment 5-2 relates to a case where, in an MU-MIMO, up toN=3 layers being classified from each other are supported for eachterminal.

Hereinafter, examples of a codeword and a DMRS antenna port numberaccording to a number of layers used of a terminal will be described.

In case of one layer, codeword 0 is enabled, and codeword 1 is disabled.The enabled codeword 0 may be mapped to any one of DMRS antenna ports#1, #2, #3, #4, #5, #6, #7, and #8. Herein, when the codeword 0 ismapped to any one of the DMRS antenna ports #2, #3, #4, #5, #6, #7, and#8, it may correspond to a case where a corresponding terminal is in anMU-MIMO.

In case of two layers, codeword 0 is enabled, and codeword 1 isdisabled. The enabled codeword 0 may be mapped to any one of DMRSantenna ports #1 and #2, #3 and #4, #5 and #6, and #7 and #8. Herein,when the codeword 0 is mapped to any one of the DMRS antenna ports #3and #4, #5 and #6, and #7 and #8, it may correspond to a case where acorresponding terminal is in an MU-MIMO.

In case of three layers, codeword 0 is enabled, and codeword 1 isdisabled. The enabled codeword 0 may be mapped to any one of DMRSantenna ports #1 to #3, and #5 to #7 (DMRS antenna ports #1˜#3, and#5˜#7). Herein, when the codeword 0 is mapped to the DMRS antenna ports#5 to #7, it may correspond to a case where a corresponding terminal isin an MU-MIMO.

Alternatively, in case of three layers, codeword 0 is enabled, andcodeword 1 is disabled. The enabled codeword 0 may be mapped to any oneof DMRS antenna ports #1 to #3, and #4 to #6 (DMRS antenna ports #1˜#3,and #4˜#6). Herein, when the codeword 0 is mapped to the DMRS antennaports #4 to #6, it may correspond to a case where a correspondingterminal is in an MU-MIMO.

In case of four layers, codeword 0 is enabled, and codeword 1 isdisabled. The enabled codeword 0 may be mapped to antenna ports #1 to #4(DMRS antenna ports #1˜#4).

In case of five layers, codeword 0 and codeword 1 are both enabled. Theenabled codeword 0 may be mapped to DMRS antenna ports #1 and #2, andthe enabled codeword 1 may be mapped to DMRS antenna ports #3 to #5(DMRS antenna ports #3˜#5).

In case of six layers, codeword 0 and codeword 1 are both enabled. Theenabled codeword 0 may be mapped to DMRS antenna ports #1 to #3 (DMRSantenna ports #1˜#3), and the enabled codeword 1 may be mapped to DMRSantenna ports #4 to #6 (DMRS antenna ports #4˜#6).

In case of seven layers, codeword 0 and codeword 1 are both enabled. Theenabled codeword 0 may be mapped to DMRS antenna ports #1 to #3 (DMRSantenna ports #1˜#3), and the enabled codeword 1 may be mapped to DMRSantenna ports #4 to #7 (DMRS antenna ports #4˜#7).

In case of eight layers, codeword 0 and codeword are both enabled. Theenabled codeword 0 may be mapped to DMRS antenna ports #1 to #4 (DMRSantenna ports #1˜#4), and the enabled codeword 1 may be mapped to DMRSantenna ports #5 to #8 (DMRS antenna ports #5˜#8).

Table 21 below shows an example of indicating an antenna port number, anumber of layers, and a number of symbols for one codeword when onecodeword is enabled and the other codeword is disabled (in other words,when codeword 0 is enabled, and codeword 1 is disabled). In other words,in the table, a specific bit value corresponds to a specific message,and the specific message indicates a combination of a number of symbols,a number of layers, and an antenna port number.

In addition, in the example of Table 52, in case of two symbols andthree layers (in other words, 2 symbol, and 3 layers), an antenna portnumber may be fixedly used when the antenna port number corresponds toone of DMRS antenna ports #5˜#7, and DMRS antenna ports #4˜#6.

TABLE 52 Bit value Message 0 1 symbol, 1 layer, DMRS antenna ports #1 11 symbol, 1 layer, DMRS antenna ports #2 2 1 symbol, 1 layer, DMRSantenna ports #3 3 1 symbol, 1 layer, DMRS antenna ports #4 4 2 symbols,1 layer, DMRS antenna ports #1 5 2 symbols, 1 layer, DMRS antenna ports#2 6 2 symbols, 1 layer, DMRS antenna ports #3 7 2 symbols, 1 layer,DMRS antenna ports #4 8 2 symbols, 1 layer, DMRS antenna ports #5 9 2symbols, 1 layer, DMRS antenna ports #6 10 2 symbols, 1 layer, DMRSantenna ports #7 11 2 symbols, 1 layer, DMRS antenna ports #8 12 1symbol, 2 layers, DMRS antenna ports #1~#2 13 1 symbol, 2 layers, DMRSantenna ports #3~#4 14 2 symbols, 2 layers, DMRS antenna ports #1~#2 152 symbols, 2 layers, DMRS antenna ports #3~#4 16 2 symbols, 2 layers,DMRS antenna ports #5~#6 17 2 symbols, 2 layers, DMRS antenna ports#7~#8 18 1 symbol, 3 layers, DMRS antenna ports #1~#3 19 2 symbols, 3layers, DMRS antenna ports #1~#3 20 2 symbols, 3 layers, DMRS antennaports #5~#7 (or #4~#6) 21 1 symbol, 4 layers, DMRS antenna ports #1~#422 2 symbols, 4 layers, DMRS antenna ports #1~#4 23 Reserved . . . . . .31 Reserved

Table 53 below shows an example of indicating a number of symbols, anantenna port number, and a number of layers for two codewords when twocodewords are both enabled (for example, when codeword 0 and codeword 1are both enabled). In other words, in the table, a specific bit valuecorresponds to a specific message, and the specific message indicates acombination of a number of symbols, a number of layers, and an antennaport number.

TABLE 53 Bit value Message 0 2 symbols, 5 layers, DMRS antenna ports#1~#5 1 2 symbols, 6 layers, DMRS antenna ports #1~#6 2 2 symbols, 7layers, DMRS antenna ports #1~#7 3 2 symbols, 8 layers, DMRS antennaports #1~#8 4 Reserved . . . . . . 31  Reserved

In order to indicate a number of symbols, a number of layers, and a DMRSantenna port number when one codeword of the Table 21 is enabled, asignaling field having a 5-bit size may be defined. The above signalingfield is sufficiently large to indicate a number of symbols, a number oflayers, and a DMRS antenna port number when two codewords of Table 22are enabled. In addition, a number of cases to be indicated forconfiguring one signaling field by combining the examples of the Table52 and the Table 53 does not exceed 32 cases, thus a signaling fieldhaving a 5-bit size may be identically used.

Table 54 below shows where a case when one codeword of the Table 21 isenabled and a case when two codewords of the Table 53 are enabled arecombined and represented in one table. The examples of the Table 52 andthe Table 53 may be used for a case where information of whether onecodeword is enabled or two codewords are enabled may be obtained inadvance. Table 54 below may be used for all cases where information of anumber of enabled codewords may be and may not be obtained (in otherwords, regardless of whether or not information of a number of enabledcodewords may be obtained).

In addition, in the example of Table 54, in case of two symbols andthree layers(in other words, 2 symbol, and 3 layers), an antenna portnumber may be fixedly used when the antenna port number corresponds toone of DMRS antenna ports #5˜#7, and DMRS antenna ports #4˜#6.

TABLE 54 Bit value Message 0 1 symbol, 1 layer, DMRS antenna ports #1,codeword 0 1 1 symbol, 1 layer, DMRS antenna ports #2, codeword 0 2 1symbol, 1 layer, DMRS antenna ports #3, codeword 0 3 1 symbol, 1 layer,DMRS antenna ports #4, codeword 0 4 2 symbols, 1 layer, DMRS antennaports #1, codeword 0 5 2 symbols, 1 layer, DMRS antenna ports #2,codeword 0 6 2 symbols, 1 layer, DMRS antenna ports #3, codeword 0 7 2symbols, 1 layer, DMRS antenna ports #4, codeword 0 8 2 symbols, 1layer, DMRS antenna ports #5, codeword 0 9 2 symbols, 1 layer, DMRSantenna ports #6, codeword 0 10 2 symbols, 1 layer, DMRS antenna ports#7, codeword 0 11 2 symbols, 1 layer, DMRS antenna ports #8, codeword 012 1 symbol, 2 layers, DMRS antenna ports #1~#2, codeword 0 13 1 symbol,2 layers, DMRS antenna ports #3~#4, codeword 0 14 2 symbols, 2 layers,DMRS antenna ports #1~#2, codeword 0 15 2 symbols, 2 layers, DMRSantenna ports #3~#4, codeword 0 16 2 symbols, 2 layers, DMRS antennaports #5~#6, codeword 0 17 2 symbols, 2 layers, DMRS antenna ports#7~#8, codeword 0 18 1 symbol, 3 layers, DMRS antenna ports #1~#3,codeword 0 19 2 symbols, 3 layers, DMRS antenna ports #1~#3, codeword 020 2 symbols, 3 layers, DMRS antenna ports #5~#7 (or #4~#6), codeword 021 1 symbol, 4 layers, DMRS antenna ports #1~#4, codeword 0 22 2symbols, 4 layers, DMRS antenna ports #1~#4, codeword 0 23 2 symbols, 5layers, DMRS antenna ports #1~#5, codeword 0 & codeword 1 24 2 symbols,6 layers, DMRS antenna ports #1~#6, codeword 0 & codeword 1 25 2symbols, 7 layers, DMRS antenna ports #1~#7, codeword 0 & codeword 1 262 symbols, 8 layers, DMRS antenna ports #1~#8, codeword 0 & codeword 127 Reserved . . . . . . 31 Reserved

Embodiment 5-3

The present embodiment 5-3 relates to a case where, in an MU-MIMO, up toN=4 layers being classified from each other are supported for eachterminal.

Hereinafter, examples of a codeword and a DMRS antenna port numberaccording to a number of layers used for each terminal will bedescribed.

In case of one layer, codeword 0 is enabled, and codeword 1 is disabled.The enabled codeword 0 may be mapped to any one DMRS antenna ports #1,#2, #3, #4, #5, #6, #7, and #8. Herein, when the codeword 0 is mapped toany one of the DMRS antenna ports #2, #3, #4, #5, #6, #7, and #8, it maycorresponds to a case where a corresponding terminal is in an MU-MIMO.

In case of two layers, codeword 0 is enabled, and codeword 1 isdisabled. The enabled codeword 0 may be mapped to any one of DMRSantenna ports #1 and #2, #3 and #4, #5 and #6, and #7 and #8. Herein,when the codeword 0 is mapped to any one of the DMRS antenna ports #3and #4, #5 and #6, and #7 and #8, it may corresponds to a case where acorresponding terminal is in an MU-MIMO.

In case of three layers, codeword 0 is enabled, and codeword 1 isdisabled. The enabled codeword 0 may be mapped to any one of DMRSantenna ports #1 to #3, and #5 to #7 (DMRS antenna ports #1˜#3, or#5˜#7). Herein, when the codeword 0 is mapped to the DMRS antenna port#5 to #7, it may correspond to a case where a corresponding terminal isin an MU-MIMO.

Alternatively, in case of three layers, codeword 0 is enabled, andcodeword 1 is disabled. The enabled codeword 0 may be mapped to any oneof DMRS antenna ports #1 to #3, and #4 to #6 (DMRS antenna ports #1˜#3,or #4˜#6). Herein, when the codeword 0 is mapped to the DMRS antennaports #4 to #6, it may correspond to a case where a correspondingterminal is in an MU-MIMO.

In case of four layers, codeword 0 is enabled, and codeword 1 isdisabled. The enabled codeword 0 may be mapped to any one of DMRSantenna ports #1 to #4, and #5 to #8 (DMRS antenna ports #1˜#4, or#5˜#8). Herein, when the codeword 0 is mapped to the DMRS antenna ports#5 to #8, it may correspond to a case where a corresponding terminal isin an MU-MIMO.

In case of five layers, codeword 0 and codeword 1 are both enabled. Theenabled codeword 0 may be mapped to DMRS antenna ports #1 and #2, andthe enabled codeword 1 may be mapped to DMRS antenna ports #3 to #5(DMRS antenna ports #3˜#5).

In case of six layers, codeword 0 and codeword 1 are both enabled. Theenabled codeword 0 may be mapped to DMRS antenna ports #1 to #3 (DMRSantenna ports #1˜#3), and the enabled codeword 1 may be mapped to DMRSantenna ports #4 to #6 (DMRS antenna ports #4˜#6).

In case of seven layers, codeword 0 and codeword 1 are both enabled. Theenabled codeword 0 may be mapped to DMRS antenna ports #1 to #3 (DMRSantenna ports #1˜#3), and the enabled codeword 1 may be mapped to DMRSantenna ports #4 to #7 (DMRS antenna ports #4˜#7).

In case of eight layers, codeword 0 and codeword 1 are both enabled. Theenabled codeword 0 may be mapped to DMRS antenna ports #1 to #4 (DMRSantenna ports #1˜#4), and the enabled codeword 1 may be mapped to DMRSantenna ports #5 to #8 (DMRS antenna ports #5˜#8).

Table 55 below shows an example of indicating a number of symbols, anumber of layers, and an antenna port number for one codeword when onecodeword is enabled and the other codeword is disabled (in other words,when codeword 0 is enabled and codeword 1 is disabled). In other words,in the table, a specific bit value corresponds to a specific message,and the specific message indicates a combination of a number of symbols,a number of layers, and an antenna port number.

In addition, in the example of Table 55, in case of two symbols andthree layers (in other words, 2 symbols, and 3 layers), an antenna portnumber may be fixedly used when the antenna port number corresponds toone of DMRS antenna ports #5˜#7, and DMRS antenna ports #4˜#6.

TABLE 55 Bit value Message 0 1 symbol, 1 layer, DMRS antenna ports #1 11 symbol, 1 layer, DMRS antenna ports #2 2 1 symbol, 1 layer, DMRSantenna ports #3 3 1 symbol, 1 layer, DMRS antenna ports #4 4 2 symbols,1 layer, DMRS antenna ports #1 5 2 symbols, 1 layer, DMRS antenna ports#2 6 2 symbols, 1 layer, DMRS antenna ports #3 7 2 symbols, 1 layer,DMRS antenna ports #4 8 2 symbols, 1 layer, DMRS antenna ports #5 9 2symbols, 1 layer, DMRS antenna ports #6 10 2 symbols, 1 layer, DMRSantenna ports #7 11 2 symbols, 1 layer, DMRS antenna ports #8 12 1symbol, 2 layers, DMRS antenna ports #1~#2 13 1 symbol, 2 layers, DMRSantenna ports #3~#4 14 2 symbols, 2 layers, DMRS antenna ports #1~#2 152 symbols, 2 layers, DMRS antenna ports #3~#4 16 2 symbols, 2 layers,DMRS antenna ports #5~#6 17 2 symbols, 2 layers, DMRS antenna ports#7~#8 18 1 symbol, 3 layers, DMRS antenna ports #1~#3 19 2 symbols, 3layers, DMRS antenna ports #1~#3 20 2 symbols, 3 layers, DMRS antennaports #5~#7 (or #4~#6) 21 1 symbol, 4 layers, DMRS antenna ports #1~#422 2 symbols, 4 layers, DMRS antenna ports #1~#4 23 2 symbols, 4 layers,DMRS antenna ports #5~#8 24 Reserved . . . . . . 31 Reserved

Table 56 below shows an example of indicating a number of symbols, anumber of layers, and an antenna port number for two codewords when twocodewords are both enabled (for example, when codeword 0 and codeword 1are both enabled). In other words, in the table, a specific bit valuecorresponds to a specific message, and the specific message indicates acombination of a number of symbols, a number of layers, and an antennaport number.

TABLE 56 Bit value Message 0 2 symbols, 5 layers, DMRS antenna ports#1~#5 1 2 symbols, 6 layers, DMRS antenna ports #1~#6 2 2 symbols, 7layers, DMRS antenna ports #1~#7 3 2 symbols, 8 layers, DMRS antennaports #1~#8 4 Reserved . . . . . . 31  Reserved

In order to indicate a number of symbols, a number of layers, and a DMRSantenna port number when one codeword of the Table 24 is enabled, asignaling field having a 5-bit size may be defined. The above signalingfield is sufficiently large to indicate a number of symbols, a number oflayers, and a DMRS antenna port number when two codewords of the Table25 are enabled. In addition, a number of cases to be indicated forconfiguring one signaling field by combining the examples of the Table55 and the Table 56 does not exceeds 32 cases, thus a signaling fieldhaving a 5-bit size may be identically used.

Table 57 below shows where a case when one codeword of the Table 55 isenabled and a case when two codewords of the Table 56 are enabled arecombined and represented in one table. The examples of the Table 55 andthe Table 56 may be used for a case where information of whether onecodeword is enabled or two codeword are enabled may be obtained inadvance. Table 57 below may be used for all cases where information of anumber of enabled codewords may be and may not be obtained (in otherwords, regardless of whether or not information of a number of enabledcodeword may be obtained).

In addition, in the example of Table 57, in case of two symbols andthree layers (in other words, 2 symbol, and 3 layers), an antenna portnumber may be fixedly used when the antenna port number corresponds toone of DMRS antenna ports #5˜#7, and DMRS antenna ports #4˜#6.

TABLE 57 Bit value Message 0 1 symbol, 1 layer, DMRS antenna ports #1,codeword 0 1 1 symbol, 1 layer, DMRS antenna ports #2, codeword 0 2 1symbol, 1 layer, DMRS antenna ports #3, codeword 0 3 1 symbol, 1 layer,DMRS antenna ports #4, codeword 0 4 2 symbols, 1 layer, DMRS antennaports #1, codeword 0 5 2 symbols, 1 layer, DMRS antenna ports #2,codeword 0 6 2 symbols, 1 layer, DMRS antenna ports #3, codeword 0 7 2symbols, 1 layer, DMRS antenna ports #4, codeword 0 8 2 symbols, 1layer, DMRS antenna ports #5, codeword 0 9 2 symbols, 1 layer, DMRSantenna ports #6, codeword 0 10 2 symbols, 1 layer, DMRS antenna ports#7, codeword 0 11 2 symbols, 1 layer, DMRS antenna ports #8, codeword 012 1 symbol, 2 layers, DMRS antenna ports #1~#2, codeword 0 13 1 symbol,2 layers, DMRS antenna ports #3~#4, codeword 0 14 2 symbols, 2 layers,DMRS antenna ports #1~#2, codeword 0 15 2 symbols, 2 layers, DMRSantenna ports #3~#4, codeword 0 16 2 symbols, 2 layers, DMRS antennaports #5~#6, codeword 0 17 2 symbols, 2 layers, DMRS antenna ports#7~#8, codeword 0 18 1 symbol, 3 layers, DMRS antenna ports #1~#3,codeword 0 19 2 symbols, 3 layers, DMRS antenna ports #1~#3, codeword 020 2 symbols, 3 layers, DMRS antenna ports #5~#7 (or #4~#6), codeword 021 1 symbol, 4 layers, DMRS antenna ports #1~#4, codeword 0 22 2symbols, 4 layers, DMRS antenna ports #1~#4, codeword 0 23 2 symbols, 4layers, DMRS antenna ports #5~#8, codeword 0 24 2 symbols, 5 layers,DMRS antenna ports #1~#5, codeword 0 & codeword 1 25 2 symbols, 6layers, DMRS antenna ports #1~#6, codeword 0 & codeword 1 26 2 symbols,7 layers, DMRS antenna ports #1~#7, codeword 0 & codeword 1 27 2symbols, 8 layers, DMRS antenna ports #1~#8, codeword 0 & codeword 1 28Reserved . . . . . . 31 Reserved

Embodiment 6

The present embodiment 6 relates to a method of configuring andindicating information of a number of layers, an antenna port number anda number of symbols of a DMRS in case of a DMRS configuration type 2 (inother words, in case of a DMRS configuration type of a CDM groupmethod).

Hereinafter, in detailed examples, examples of a combination of a numberof layers, an antenna port number, and a number of symbols of a DMRS maybe represented in one table form, and a value indicating a specificcombination among combinations configured as the above table form may betransmitted from the base station to the terminal by using DCI. In otherwords, in a DCI format, as an example below, a signaling fieldindicating a number of layers, an antenna port number, and a number ofsymbols of a DMRS may be defined. When a correspond signaling field hasa specific value, a number of layers, an antenna port number, and anumber of symbols of a DMRS which is mapped to the specific value may beindicated.

In addition, in detailed examples below, it is assumed that up to twocodewords are used in an NR system. In detail, it is assumed that, foreach terminal, one codeword (for example, codeword 0) is used when oneto four layers are used, and two codewords (for example, codeword 0 andcodeword 1) are used when five to eight layers are used. In addition, itis assumed that one codeword may be mapped to up to four layers, and onelayer is mapped to one antenna port.

In addition, in detailed examples below, an order of bit valuesrepresented in the table is not limited thereto, the order may be out oforder, and a message may be identical. In other words, in the presentdisclosure, a mapping relation between a bit value and a message is notrestricted. In addition, a detailed content of a message may bereferenced with FIGS. 13 to 17, and Tables 33 to 48.

Embodiment 6-1

The present embodiment 6-1 relates to a case where, in an MU-MIMO, up toN=2 layers being classified from each other are supported for eachterminal. Hereinafter, a codeword and a DMRS antenna port numberaccording to a number of layers used for each terminal will bedescribed.

In case of one layer, codeword 0 is enabled, and codeword 1 is disabled.The enabled codeword 0 may be mapped to any one of DMRS antenna ports#1, #2, #3, #4, #5, #6, #7, and #8. Herein, when the codeword 0 ismapped to the DMRS antenna ports #2, #3, #4, #5, #6, #7, and #8, it maycorrespond to a case where a corresponding terminal is in an MU-MIMO.

In case of two layers, codeword 0 is enabled, and codeword 1 isdisabled. The enabled codeword 0 may be mapped to any one of DMRSantenna ports #1 and #2, #3 and #4, #5 and #6, and #7 and #8. Herein,when the codeword 0 is mapped to any one of the DMRS antenna ports #3and #4, #5 and #6, and #7 and #8, it may correspond to a case where acorresponding terminal is in an MU-MIMO.

In case of three layers, codeword 0 is enabled, and codeword 1 isdisabled. The enabled codeword 0 may be mapped to DMRS antenna ports #1to #3 (DMRS antenna ports #1˜#3).

In case of four layers, codeword 0 is enabled, and codeword 1 isdisabled. The enabled codeword 0 may be mapped to DMRS antenna ports #1to #4 (DMRS antenna ports #1˜#4).

In case of five layers, codeword 0 and codeword 1 are all enabled. Theenabled codeword 0 may be mapped to DMRS antenna ports #1 and #2, andthe enabled codeword 1 may be mapped to DMRS antenna ports #3 to #5(DMRS antenna ports #3˜#5).

In case of six layers, codeword 0 and codeword 1 are both enabled. Theenabled codeword 0 may be mapped to DMRS antenna ports #1 to #3 (DMRSantenna ports #1˜#3), and the enabled codeword 1 may be mapped to DMRSantenna ports #4 to #6 (DMRS antenna ports #4˜#6).

In case of seven layers, codeword 0 and codeword 1 are both enabled. Theenabled codeword 0 may be mapped to DMRS antenna ports #1 to #3 (DMRSantenna ports #1˜#3), and the enabled codeword 1 may be mapped to DMRSantenna ports #4 to #7 (DMRS antenna ports #4˜#7).

In case of eight layers, codeword 0 and codeword 1 are both enabled. Theenabled codeword 0 may be mapped to DMRS antenna ports #1 to #4 (DMRSantenna ports #1˜#4), and the enabled codeword 1 may be mapped to DMRSantenna ports #5 to #8 (DMRS antenna ports #5˜#8).

Table 58 below shows an example of indicating a number of symbols, anumber of layers, and a antenna port number for one codeword when onecodeword is enabled and the other codeword is disabled (in other words,when codeword 0 is enabled, and codeword 1 is disabled). In other words,in the table, a specific bit value corresponds to a specific message,and the specific message indicates a combination of a number of symbols,a number of layers, and an antenna port number.

TABLE 58 Bit value Message 0 1 symbol, 1 layer, DMRS antenna ports #1 11 symbol, 1 layer, DMRS antenna ports #2 2 1 symbol, 1 layer, DMRSantenna ports #3 3 1 symbol, 1 layer, DMRS antenna ports #4 4 1 symbol,1 layer, DMRS antenna ports #5 5 1 symbol, 1 layer, DMRS antenna ports#6 6 2 symbols, 1 layer, DMRS antenna ports #1 7 2 symbols, 1 layer,DMRS antenna ports #2 8 2 symbols, 1 layer, DMRS antenna ports #3 9 2symbols, 1 layer, DMRS antenna ports #4 10 2 symbols, 1 layer, DMRSantenna ports #5 11 2 symbols, 1 layer, DMRS antenna ports #6 12 2symbols, 1 layer, DMRS antenna ports #7 13 2 symbols, 1 layer, DMRSantenna ports #8 14 2 symbols, 1 layer, DMRS antenna ports #9 15 2symbols, 1 layer, DMRS antenna ports #10 16 2 symbols, 1 layer, DMRSantenna ports #11 17 2 symbols, 1 layer, DMRS antenna ports #12 18 1symbol, 2 layers, DMRS antenna ports #1~#2 19 1 symbol, 2 layers, DMRSantenna ports #3~#4 20 1 symbol, 2 layers, DMRS antenna ports #5~#6 21 2symbols, 2 layers, DMRS antenna ports #1~#2 22 2 symbols, 2 layers, DMRSantenna ports #3~#4 23 2 symbols, 2 layers, DMRS antenna ports #5~#6 242 symbols, 2 layers, DMRS antenna ports #7~#8 25 2 symbols, 2 layers,DMRS antenna ports #9~#10 26 2 symbols, 2 layers, DMRS antenna ports#11~#12 27 1 symbol, 3 layers, DMRS antenna ports #1~#3 28 2 symbols, 3layers, DMRS antenna ports #1~#3 29 1 symbol, 4 layers, DMRS antennaports #1~#4 30 2 symbols, 4 layers, DMRS antenna ports #1~#4 31 Reserved

Table 59 below shows an example of indicating a number of symbols, anumber of layers, and an antenna port number for two codewords when twocodewords are enabled (for example, when codeword 0 and codeword 1 bothall enabled). In other words, in the table, a specific bit valuecorresponds to a specific message, and the specific message indicates acombination of a number of symbols, a number of layers, and an antennaport number.

TABLE 59 Bit value Message 0 1 symbols, 5 layers, DMRS antenna ports#1~#5 1 2 symbols, 5 layers, DMRS antenna ports #1~#5 2 1 symbols, 6layers, DMRS antenna ports #1~#6 3 2 symbols, 6 layers, DMRS antennaports #1~#6 4 2 symbols, 7 layers, DMRS antenna ports #1~#7 5 2 symbols,8 layers, DMRS antenna ports #1~#8 6 Reserved . . . . . . 31  Reserved

In order to indicate a number of symbols, a number of layers, and a DMRSantenna port number when one codeword of the Table 58 is enabled, asignaling field having a 5-bit size may be defined. The above signalingfield is sufficiently large to indicate a number of symbols, a number oflayers, and a DMRS antenna port number when two codewords of the Table59 are enabled. Meanwhile, a case to be indicated for configuring onesignaling field by combining the examples of the Tables 58 and 59exceeds 32 cases, thus a signaling field having a 5-bit size may not beidentically used. Accordingly, in the above cases, the signaling fieldmay not be configured by simply combining massages of Tables 58 and 59,and a signaling field having a 5-bit size may be used by configuring theentire cases being equal to or less than 32 cases by excluding a part ofthe message of Tables 58 and 59. Alternatively, in order to include allmessages of Tables 58 and 59 (in other words, in order to includes 37messages), a signaling field having a 6-bit size may be newly defined.

Embodiment 6-2

The present embodiment 6-2 relates to a case where, in an MU-MIMO, up toN=3 layers being classified from each other are supported for eachterminal.

Hereinafter, examples of a codeword and a DMRS antenna port numberaccording to a number of layers used for each terminal will bedescribed.

In case of one layer, codeword 0 is enabled, and codeword 1 is disabled.The enabled codeword 0 may be mapped to any one of DMRS antenna ports#1, #2, #3, #4, #5, #6, #7, and #8. Herein, when the codeword 0 ismapped to nay one of the DMRS antenna ports #2, #3, #4, #5, #6, #7, and#8, it may correspond to a case where a corresponding terminal is in anMU-MIMO.

In case of two layers, codeword 0 is enabled, and codeword 1 isdisabled. The enabled codeword 0 may be mapped to any one of DMRSantenna ports #1 and #2, #3 and #4, #5 and #6, and #7 and #8. Herein,when the codeword 0 is mapped to any one of the DMRS antenna ports #3and #4, #5 and #6, and #7 and #8, it may correspond to a case where acorresponding terminal is in an MU-MIMO.

In case of three layers, codeword 0 is enabled, and codeword 1 isdisabled. The enabled codeword 0 may be mapped to any one of DMRSantenna ports #1 to #3, #4 to #6, #7 to #9, and #10 to #12 (DMRS antennaports #1˜#3, #4˜#6, #7˜#9, or #10˜#12). Herein, when the codeword 0 ismapped to any one of the DMRS antenna ports #4 to #6, #7 to #9, and #10to #12 (DMRS antenna ports #4˜#6, #7˜#9, or #10˜#12), it may correspondto a case where a corresponding terminal is in an MU-MIMO.

In case of four layers, codeword 0 is enabled, and codeword 1 isdisabled. The enabled codeword 0 may be mapped to DMRS antenna ports #1to #4 (DMRS antenna ports #1˜#4).

In case of five layers, codeword 0 and codeword 1 are both enabled. Theenabled codeword 0 may be mapped to DMRS antenna ports #1 and #2, andthe enabled codeword 1 may be mapped to DMRS antenna ports #3 to #5(DMRS antenna ports #3˜#5).

In case of six layers, codeword 0 and codeword 1 are both enabled. Theenabled codeword 0 may be mapped to DMRS antenna ports #1 to #3 (DMRSantenna ports #1˜#3), and the enabled codeword 1 may be mapped to DMRSantenna ports #4 to #6 (DMRS antenna ports #4˜#6).

In case of seven layers, codeword 0 and codeword 1 are both enabled. Theenabled codeword 0 may be mapped to DMRS antenna ports #1 to #3 (DMRSantenna ports #1˜#3), and the enabled codeword 1 may be mapped to DMRSantenna ports #4 to #7 (DMRS antenna ports #4˜#7).

In case of eight layers, codeword 0 and codeword 1 are both enabled. Theenabled codeword 0 may be mapped to DMRS antenna ports #1 to #4 (DMRSantenna ports #1˜#4), and the enabled codeword 1 may be mapped to DMRSantenna ports #5 to #8 (DMRS antenna ports #5˜#8).

Table 60 below shows an example of indicating a number of symbols, anumber of layers, and an antenna port number for one codeword when onecodeword is enabled and the other codeword is disabled (in other words,when codeword 0 is enabled, and codeword 1 is disabled). In other words,in the table, a specific bit value corresponds to a specific message,and the specific message indicates a combination of a number of symbols,a number of layers, and an antenna port number.

TABLE 60 Bit value Message 0 1 symbol, 1 layer, DMRS antenna ports #1 11 symbol, 1 layer, DMRS antenna ports #2 2 1 symbol, 1 layer, DMRSantenna ports #3 3 1 symbol, 1 layer, DMRS antenna ports #4 4 1 symbol,1 layer, DMRS antenna ports #5 5 1 symbol, 1 layer, DMRS antenna ports#6 6 2 symbols, 1 layer, DMRS antenna ports #1 7 2 symbols, 1 layer,DMRS antenna ports #2 8 2 symbols, 1 layer, DMRS antenna ports #3 9 2symbols, 1 layer, DMRS antenna ports #4 10 2 symbols, 1 layer, DMRSantenna ports #5 11 2 symbols, 1 layer, DMRS antenna ports #6 12 2symbols, 1 layer, DMRS antenna ports #7 13 2 symbols, 1 layer, DMRSantenna ports #8 14 2 symbols, 1 layer, DMRS antenna ports #9 15 2symbols, 1 layer, DMRS antenna ports #10 16 2 symbols, 1 layer, DMRSantenna ports #11 17 2 symbols, 1 layer, DMRS antenna ports #12 18 1symbol, 2 layers, DMRS antenna ports #1~#2 19 1 symbol, 2 layers, DMRSantenna ports #3~#4 20 1 symbol, 2 layers, DMRS antenna ports #5~#6 21 2symbols, 2 layers, DMRS antenna ports #1~#2 22 2 symbols, 2 layers, DMRSantenna ports #3~#4 23 2 symbols, 2 layers, DMRS antenna ports #5~#6 242 symbols, 2 layers, DMRS antenna ports #7~#8 25 2 symbols, 2 layers,DMRS antenna ports #9~#10 26 2 symbols, 2 layers, DMRS antenna ports#11~#12 27 1 symbol, 3 layers, DMRS antenna ports #1~#3 28 1 symbol, 3layers, DMRS antenna ports #4~#6 29 2 symbols, 3 layers, DMRS antennaports #1~#3 30 2 symbols, 3 layers, DMRS antenna ports #4~#6 31 2symbols, 3 layers, DMRS antenna ports #7~#9 32 2 symbols, 3 layers, DMRSantenna ports #10~#12 33 1 symbol, 4 layers, DMRS antenna ports #1~#4 342 symbols, 4 layers, DMRS antenna ports #1~#4 35 Reserved . . . . . . 63Reserved

Table 61 below shows an example of indicating a number of symbols, anumber of layers, and an antenna port number for two codewords when twocodewords are both enabled (for example, when codeword 0 and codeword 1are both enabled). In other words, in the table, a specific bit valuecorresponds to a specific message, and the specific message indicates acombination of a number of symbols, a number of layers, and an antennaport number.

TABLE 61 Bit value Message 0 1 symbols, 5 layers, DMRS antenna ports#1~#5 1 2 symbols, 5 layers, DMRS antenna ports #1~#5 2 1 symbols, 6layers, DMRS antenna ports #1~#6 3 2 symbols, 6 layers, DMRS antennaports #1~#6 4 2 symbols, 7 layers, DMRS antenna ports #1~#7 5 2 symbols,8 layers, DMRS antenna ports #1~#8 6 Reserved . . . . . . 63  Reserved

In order to indicate a number of symbols, a number of layers, and a DMRSantenna port number when one codeword of the Table 60 is enabled, asignaling field having a 6-bit size may be defined. The above signalingfield is sufficiently large to indicate a number of symbols, a number oflayers, and a DMRS antenna port number when two codewords of the Table30 are enabled. In addition, a case to be indicated for configuring onesignaling field by combining the examples of the Tables 60 and 61 doesnot exceed 64 cases, thus a signaling field having a 6-bit size may beidentically used.

Table 62 below shows where a case where one codeword of the Table 60 isenabled and a case where two codewords of the Table 61 are combined andrepresented in one table. The examples of the Tables 60 and 61 may beused for a case where information of whether one codeword is enabled ortwo codewords are enabled may be obtained in advance. Table 62 below maybe used for all cases where information of a number of enabled codewordsmay be and may not be obtained (in other words, regardless of whether ornot information of a number of enabled codewords may be obtained).

TABLE 62 Bit value Message 0 1 symbol, 1 layer, DMRS antenna ports #1,codeword 0 1 1 symbol, 1 layer, DMRS antenna ports #2, codeword 0 2 1symbol, 1 layer, DMRS antenna ports #3, codeword 0 3 1 symbol, 1 layer,DMRS antenna ports #4, codeword 0 4 1 symbol, 1 layer, DMRS antennaports #5, codeword 0 5 1 symbol, 1 layer, DMRS antenna ports #6,codeword 0 6 2 symbols, 1 layer, DMRS antenna ports #1, codeword 0 7 2symbols, 1 layer, DMRS antenna ports #2, codeword 0 8 2 symbols, 1layer, DMRS antenna ports #3, codeword 0 9 2 symbols, 1 layer, DMRSantenna ports #4, codeword 0 10 2 symbols, 1 layer, DMRS antenna ports#5, codeword 0 11 2 symbols, 1 layer, DMRS antenna ports #6, codeword 012 2 symbols, 1 layer, DMRS antenna ports #7, codeword 0 13 2 symbols, 1layer, DMRS antenna ports #8, codeword 0 14 2 symbols, 1 layer, DMRSantenna ports #9, codeword 0 15 2 symbols, 1 layer, DMRS antenna ports#10, codeword 0 16 2 symbols, 1 layer, DMRS antenna ports #11, codeword0 17 2 symbols, 1 layer, DMRS antenna ports #12, codeword 0 18 1 symbol,2 layers, DMRS antenna ports #1~#2, codeword 0 19 1 symbol, 2 layers,DMRS antenna ports #3~#4, codeword 0 20 1 symbol, 2 layers, DMRS antennaports #5~#6, codeword 0 21 2 symbols, 2 layers, DMRS antenna ports#1~#2, codeword 0 22 2 symbols, 2 layers, DMRS antenna ports #3~#4,codeword 0 23 2 symbols, 2 layers, DMRS antenna ports #5~#6, codeword 024 2 symbols, 2 layers, DMRS antenna ports #7~#8, codeword 0 25 2symbols, 2 layers, DMRS antenna ports #9~#10, codeword 0 26 2 symbols, 2layers, DMRS antenna ports #11~#12, codeword 0 27 1 symbol, 3 layers,DMRS antenna ports #1~#3, codeword 0 28 1 symbol, 3 layers, DMRS antennaports #4~#6, codeword 0 29 2 symbols, 3 layers, DMRS antenna ports#1~#3, codeword 0 30 2 symbols, 3 layers, DMRS antenna ports #4~#6,codeword 0 31 2 symbols, 3 layers, DMRS antenna ports #7~#9, codeword 032 2 symbols, 3 layers, DMRS antenna ports #10~#12, codeword 0 33 1symbol, 4 layers, DMRS antenna ports #1~#4, codeword 0 34 2 symbols, 4layers, DMRS antenna ports #1~#4, codeword 0 35 1 symbols, 5 layers,DMRS antenna ports #1~#5, codeword 0 & codeword 1 36 2 symbols, 5layers, DMRS antenna ports #1~#5, codeword 0 & codeword 1 37 1 symbols,6 layers, DMRS antenna ports #1~#6, codeword 0 & codeword 1 38 2symbols, 6 layers, DMRS antenna ports #1~#6, codeword 0 & codeword 1 392 symbols, 7 layers, DMRS antenna ports #1~#7, codeword 0 & codeword 140 2 symbols, 8 layers, DMRS antenna ports #1~#8, codeword 0 & codeword1 41 Reserved . . . . . . 63 Reserved

Embodiment 6-3

The present embodiment 6-3 relates to a case where, in an MU-MIMO, up toN=4 layers being classified from each other are supported to eachterminal.

Hereinafter, examples of a codeword and a DMRS antenna port numberaccording to a number of layers used for each terminal will bedescribed.

In case of one layer, codeword 0 is enabled, and codeword 1 is disabled.The enabled codeword 0 may be mapped to any one of DMRS antenna ports#1, #2, #3, #4, #5, #6, #7, and #8. Herein, when the codeword 0 ismapped to any one of the DMRS antenna ports #2, #3, #4, #5, #6, #7, and#8, it may correspond to a case where a corresponding terminal is in anMU-MIMO.

In case of two layers, codeword 0 is enabled, and codeword 1 isdisabled. The enabled codeword 0 may be mapped to any one of DMRSantenna ports #1 and #2, #3 and #4, #5 and #6, and #7 and #8. Herein,when the codeword 0 is mapped to any one of the DMRS antenna ports #3and #4, #5 and #6, and #7 and #8, it may correspond to a case where acorresponding terminal is in an MU-MIMO.

In case of three layers, codeword 0 is enabled, and codeword 1 isdisabled. The enabled codeword 0 may be mapped to any one of DMRSantenna ports #1 to #3, #4 to #6, #7 to #9, and #10 to #12 (DMRS antennaports #1˜#3, #4˜#6, #7˜#9, or #10˜#12). Herein, when the codeword 0 ismapped to any one of the DMRS antenna ports #4 to #6, #7 to #9, and #10to #12 (DMRS antenna ports #4˜#6, #7˜#9, or #10˜#12), it may correspondto a case where a corresponding terminal is in an MU-MIMO.

In case of four layers, codeword 0 is enabled, and codeword 1 isdisabled. The enabled codeword 0 may be mapped to any one of DMRSantenna ports #1 to #4, #5 to #8, and #9 to #12 (DMRS antenna ports#1˜#4, #5˜#8, or #9˜#12). Herein, when the codeword 0 is mapped to anyone of the DMRS antenna ports #5 to #8, and #9 to #12 (DMRS antennaports #5˜#8, or #9˜#12), it may correspond to a case where acorresponding terminal is in an MU-MIMO.

In case of five layers, codeword 0 and codeword 1 are both enabled. Theenabled codeword 0 may be mapped to DMRS antenna ports #1 and #2, andthe enabled codeword 1 may be mapped to DMRS antenna ports #3 to #5(DMRS antenna ports #3˜#5). In case of six layers, codeword 0 andcodeword 1 are both enabled. The enabled codeword 0 may be mapped toDMRS antenna ports #1 to #3 (DMRS antenna ports #1˜#3), and the enabledcodeword 1 may be mapped to DMRS antenna ports #4 to #6 (DMRS antennaports #4˜#6).

In case of seven layers, codeword 0 and codeword 1 are both enabled. Theenabled codeword 0 may be mapped to DMRS antenna ports #1 to #3 (DMRSantenna ports #1˜#3), and the enabled codeword 1 may be mapped to DMRSantenna ports #4 to #7 (DMRS antenna ports #4˜#7).

In case of eight layers, codeword 0 and codeword 1 are both enabled. Theenabled codeword 0 may be mapped to DMRS antenna ports #1 to #4 (DMRSantenna ports #1˜#4), and the enabled codeword 1 may be mapped to DMRSantenna ports #5 to #8 (DMRS antenna ports #5˜#8).

Table 63 below shows an example of indicating a number of symbols, anumber of layers, and an antenna port number for one codeword when onecodeword is enabled and the other codeword is disabled (in other words,when codeword 0 is enabled, and codeword 1 is disabled). In other words,in the table, a specific bit value corresponds to a specific message,and the specific message indicates a combination of a number of symbols,a number of layers, and an antenna port number.

TABLE 63 Bit value Message 0 1 symbol, 1 layer, DMRS antenna ports #1 11 symbol, 1 layer, DMRS antenna ports #2 2 1 symbol, 1 layer, DMRSantenna ports #3 3 1 symbol, 1 layer, DMRS antenna ports #4 4 1 symbol,1 layer, DMRS antenna ports #5 5 1 symbol, 1 layer, DMRS antenna ports#6 6 2 symbols, 1 layer, DMRS antenna ports #1 7 2 symbols, 1 layer,DMRS antenna ports #2 8 2 symbols, 1 layer, DMRS antenna ports #3 9 2symbols, 1 layer, DMRS antenna ports #4 10 2 symbols, 1 layer, DMRSantenna ports #5 11 2 symbols, 1 layer, DMRS antenna ports #6 12 2symbols, 1 layer, DMRS antenna ports #7 13 2 symbols, 1 layer, DMRSantenna ports #8 14 2 symbols, 1 layer, DMRS antenna ports #9 15 2symbols, 1 layer, DMRS antenna ports #10 16 2 symbols, 1 layer, DMRSantenna ports #11 17 2 symbols, 1 layer, DMRS antenna ports #12 18 1symbol, 2 layers, DMRS antenna ports #1~#2 19 1 symbol, 2 layers, DMRSantenna ports #3~#4 20 1 symbol, 2 layers, DMRS antenna ports #5~#6 21 2symbols, 2 layers, DMRS antenna ports #1~#2 22 2 symbols, 2 layers, DMRSantenna ports #3~#4 23 2 symbols, 2 layers, DMRS antenna ports #5~#6 242 symbols, 2 layers, DMRS antenna ports #7~#8 25 2 symbols, 2 layers,DMRS antenna ports #9~#10 26 2 symbols, 2 layers, DMRS antenna ports#11~#12 27 1 symbol, 3 layers, DMRS antenna ports #1~#3 28 1 symbol, 3layers, DMRS antenna ports #4~#6 29 2 symbols, 3 layers, DMRS antennaports #1~#3 30 2 symbols, 3 layers, DMRS antenna ports #4~#6 31 2symbols, 3 layers, DMRS antenna ports #7~#9 32 2 symbols, 3 layers, DMRSantenna ports #10~#12 33 1 symbol, 4 layers, DMRS antenna ports #1~#4 342 symbols, 4 layers, DMRS antenna ports #1~#4 35 2 symbols, 4 layers,DMRS antenna ports #5~#8 36 2 symbols, 4 layers, DMRS antenna ports#9~#12 37 Reserved . . . . . . 63 Reserved

Table 64 below shows an example of indicating a number of symbols, anumber of layers, and an antenna port number when two codewords are bothenabled (for example, codeword 0 and codeword 1 are both enabled). Inother words, in the table, a specific bit value corresponds to aspecific message, and the specific message indicates a combination of anumber of symbols, a number of layers, and an antenna port number.

TABLE 64 Bit value Message 0 1 symbols, 5 layers, DMRS antenna ports#1~#5 1 2 symbols, 5 layers, DMRS antenna ports #1~#5 2 1 symbols, 6layers, DMRS antenna ports #1~#6 3 2 symbols, 6 layers, DMRS antennaports #1~#6 4 2 symbols, 7 layers, DMRS antenna ports #1~#7 5 2 symbols,8 layers, DMRS antenna ports #1~#8 6 Reserved . . . . . . 63  Reserved

In order to indicate a number of symbols, a number of layers, and a DMRSantenna port number when one codeword of the Table 63 is enabled, asignaling field having a 6-bit size may be defined. The above signalingfield is sufficiently large to indicate a number of symbols, a number oflayers, and a DMRS antenna port number when two codewords of the Table64 are enabled. In addition, a number of cases to be indicated forconfiguring one signaling field by combining the examples of Tables 63and 64 which does not exceed 64 cases, thus a signaling field having a6-bit size may be identically used.

Table 65 below shows where a case where one codeword of the Table 63 isenabled and a case where two codewords of the Table 64 are enabled arecombined and represented in one table. The examples of the Tables 63 and64 may be used for a case where information of whether one codeword isenabled or two codeword are enabled may be obtained in advance. Table 65below may be used for all cases where information of a number of enabledcodewords may be, and may not be obtained (in other words, regardless ofwhether or not information of a number of enabled codewords may beobtained.

TABLE 65 Bit value Message 0 1 symbol, 1 layer, DMRS antenna ports #1,codeword 0 1 1 symbol, 1 layer, DMRS antenna ports #2, codeword 0 2 1symbol, 1 layer, DMRS antenna ports #3, codeword 0 3 1 symbol, 1 layer,DMRS antenna ports #4, codeword 0 4 1 symbol, 1 layer, DMRS antennaports #5, codeword 0 5 1 symbol, 1 layer, DMRS antenna ports #6,codeword 0 6 2 symbols, 1 layer, DMRS antenna ports #1, codeword 0 7 2symbols, 1 layer, DMRS antenna ports #2, codeword 0 8 2 symbols, 1layer, DMRS antenna ports #3, codeword 0 9 2 symbols, 1 layer, DMRSantenna ports #4, codeword 0 10 2 symbols, 1 layer, DMRS antenna ports#5, codeword 0 11 2 symbols, 1 layer, DMRS antenna ports #6, codeword 012 2 symbols, 1 layer, DMRS antenna ports #7, codeword 0 13 2 symbols, 1layer, DMRS antenna ports #8, codeword 0 14 2 symbols, 1 layer, DMRSantenna ports #9, codeword 0 15 2 symbols, 1 layer, DMRS antenna ports#10, codeword 0 16 2 symbols, 1 layer, DMRS antenna ports #11, codeword0 17 2 symbols, 1 layer, DMRS antenna ports #12, codeword 0 18 1 symbol,2 layers, DMRS antenna ports #1~#2, codeword 0 19 1 symbol, 2 layers,DMRS antenna ports #3~#4, codeword 0 20 1 symbol, 2 layers, DMRS antennaports #5~#6, codeword 0 21 2 symbols, 2 layers, DMRS antenna ports#1~#2, codeword 0 22 2 symbols, 2 layers, DMRS antenna ports #3~#4,codeword 0 23 2 symbols, 2 layers, DMRS antenna ports #5~#6, codeword 024 2 symbols, 2 layers, DMRS antenna ports #7~#8, codeword 0 25 2symbols, 2 layers, DMRS antenna ports #9~#10, codeword 0 26 2 symbols, 2layers, DMRS antenna ports #11~#12, codeword 0 27 1 symbol, 3 layers,DMRS antenna ports #1~#3, codeword 0 28 1 symbol, 3 layers, DMRS antennaports #4~#6, codeword 0 29 2 symbols, 3 layers, DMRS antenna ports#1~#3, codeword 0 30 2 symbols, 3 layers, DMRS antenna ports #4~#6,codeword 0 31 2 symbols, 3 layers, DMRS antenna ports #7~#9, codeword 032 2 symbols, 3 layers, DMRS antenna ports #10~#12, codeword 0 33 1symbol, 4 layers, DMRS antenna ports #1~#4, codeword 0 34 2 symbols, 4layers, DMRS antenna ports #1~#4, codeword 0 35 2 symbols, 4 layers,DMRS antenna ports #5~#8, codeword 0 36 2 symbols, 4 layers, DMRSantenna ports #9~#12, codeword 0 37 1 symbols, 5 layers, DMRS antennaports #1~#5, codeword 0 & codeword 1 38 2 symbols, 5 layers, DMRSantenna ports #1~#5, codeword 0 & codeword 1 39 1 symbols, 6 layers,DMRS antenna ports #1~#6, codeword 0 & codeword 1 40 2 symbols, 6layers, DMRS antenna ports #1~#6, codeword 0 & codeword 1 41 2 symbols,7 layers, DMRS antenna ports #1~#7, codeword 0 & codeword 1 42 2symbols, 8 layers, DMRS antenna ports #1~#8, codeword 0 & codeword 1 43Reserved . . . . . . 63 Reserved

Embodiment 7

The present embodiment 7 relates to method of using a combination ofdetailed examples of the above embodiment 5 and the embodiment 6.

The embodiment 5-1, the embodiment 5-2, and the embodiment 5-3 areembodiment in consideration with a DMRS configuration type 1 based on anIFDMA method. Meanwhile, the embodiment 6-1, the embodiment 6-2, and theembodiment 6-3 are embodiments in consideration with a DMRSconfiguration type 2 based on a CDM group method.

Accordingly, when it is indicated that a DMRS configuration type 1 isused by using high layer signaling such as RRC, a signaling fieldrelated to configure a DMRS and which is included in DCI may be fixedlyused according to one of the embodiment 5-1, embodiment 5-2, andembodiment 5-3. Meanwhile, when it is indicated that a DMRSconfiguration type 2 is used by using high layer signaling such as RRC,a signaling field related to configure a DMRS and which is included inDCI may be fixedly used according to one of the embodiment 6-1, theembodiment 6-2, and embodiment 6-3.

Herein, a combination configured with one of the embodiment 5-1, theembodiment 5-2, and embodiment 5-3, and one of the embodiment 6-1, theembodiment 6-2, and the embodiment 6-3 may be fixedly used.

For example, it is assumed that, in an MU-MIMO, for each terminal, up toN=2 layers are identically classified for a DMRS configuration type 1and a DMRS configuration type 2. Herein, in case of the DMRSconfiguration type 1, a signaling field related to configure a DMRS andwhich is included in DCI (for example, a signaling field having a 5-bitsize according to Tables 49 and 50) may be configured. In case of theDMRS configuration type 2, a signaling field related to configure a DMRSand which is included in DCI (for example, a signaling field having a5-bit size according to Tables 58 and 59) may be configured.

As an additional example, in a DMRS configuration type 1 and a DMRSconfiguration type 2, it is assumed that, in an MU-MIMO, a maximumnumber of available layers that may be classified and transmitted at thesame time for each terminal is different from each other. For example,it may be assumed that, in a DMRS configuration type 1, in an MU-MIMO,up to N=2 layers are classified for each terminal, and in a DMRSconfiguration type 2, in an MU-MIMO, up to N=3 layers are classified foreach terminal.

The above assumption considers that, in case of a DMRS configurationtype 1, a number of available layers that may be classified andtransmitted at the same time for across all terminals in an MU-MIMO isup to four layers in case of one symbol, and up to eight layers in caseof two symbols. The above four and eight layers are in considerationwith a maximum number of available layers that may be transmitted at thesame time for each terminal which is a multiple of N=2. In addition, incase of a DMRS configuration type 2, in an MU-MIMO, a number ofavailable layers that may be classified and transmitted at the same timefor across all terminals is up to six layers in case of one symbol, andup to twelve layers in case of two symbols. The above six and twelvelayers are in consideration with a maximum number of available layersthat may be transmitted at the same time for each terminal which is amultiple of N=3.

For example, when it is assumed that, in a DMRS configuration type 1, inan MU-MIMO, up to N=2 layers are classified for each terminal, and in aDMRS configuration type 2, in an MU-MIMO, up to N=3 layers areclassified for each terminal, a signaling field related to configure aDMRS and which is fixedly used according to a DMRS configuration typemay be configured as examples below.

Embodiment 7-1

In case of a DMRS configuration type 2, a signaling field related toconfigure a DMRS and which is included in DCI may be configuredaccording to the embodiment 6-2. In other words, in the embodiment 6-2,a signaling field having a 6-bit size may be configured according toTables 60 and 61.

In case of a DMRS configuration type 1, a signaling field related toconfigure a DMRS and which is included in DCI may be configuredaccording to the embodiment 5-1. Herein, Tables 49 and 50 of theembodiment 5-1 correspond to a signaling field having a 5-bit size.However, in case of a DMRS configuration type 2, a size of a signalingfield according to the embodiment 6-2 may be configured to have a sizeidentical to 6 bits. For this, for respective Tables 49 and 50, areserved bit corresponding to bit values from 32 to 63 may be added sothat a size of a signaling field may be configured to be a 6-bit size.

Accordingly, a size of a signaling field related to configure a DMRS andwhich is included in DCI is maintained to be identical for DMRSconfiguration types different from each other, thus it may prevent for aDCI size that is transmitted to a terminal from being changed accordingto a configuration type.

Embodiment 7-2

In case of a DMRS configuration type 1, a signaling field related toconfigure a DMRS and which is included in DCI may be configuredaccording to the embodiment 5-1. In other words, in the embodiment 5-1,a signaling field having 5-bit size according to Tables 49 and 50 may beconfigured.

In case of a DMRS configuration type 2, a signaling field related toconfigure a DMRS and which is included in DCI may be configuredaccording to the embodiment 6-2. Herein, in the embodiment 6-2, Tables60 and 61 correspond to a signaling field having a 6-bit size. However,the signaling field may be configured to have a size identical to a5-bit size of the signaling field according to the embodiment 5-1 of theDMRS configuration type 1. For this, for Table 61, by excluding bitvalues from 32 to 63 which correspond to reserved messages, a signalingfield having a 5-bit size may be configured.

Then, for Table 60, by excluding a part among 35 messages excluding areserved message, a signaling field having a 5-bit size may beconfigured.

Tables 66 to 68 below shows examples of configuring a signaling fieldrelated to configure a DMRS and which is included in DCI to have a 5-bitsize by excluding partial messages in the example of Table 60. Forexample, among 35 messages excluding a reserved bit of Table 60, threemessages having a low possibility when actually configuring a DMRS areexcluded, and a signaling field indicating one of the remaining 32messages may be configured. Tables 66 to 68 below are not restrictiveexamples, an example in which other message is excluded in Tables 66 to68 rather than the above three messages is included in a range of thepresent disclosure.

In the examples of Tables 66 to 68, example messages excluded in theexample of Table 60 are represented as “[[excluded]]”. In addition, abit value corresponding to the excluded message is not assigned.

TABLE 66 Bit value Message 0 1 symbol, 1 layer, DMRS antenna ports #1 11 symbol, 1 layer, DMRS antenna ports #2 2 1 symbol, 1 layer, DMRSantenna ports #3 3 1 symbol, 1 layer, DMRS antenna ports #4 4 1 symbol,1 layer, DMRS antenna ports #5 5 1 symbol, 1 layer, DMRS antenna ports#6 6 2 symbols, 1 layer, DMRS antenna ports #1 7 2 symbols, 1 layer,DMRS antenna ports #2 8 2 symbols, 1 layer, DMRS antenna ports #3 9 2symbols, 1 layer, DMRS antenna ports #4 10 2 symbols, 1 layer, DMRSantenna ports #5 11 2 symbols, 1 layer, DMRS antenna ports #6 12 2symbols, 1 layer, DMRS antenna ports #7 13 2 symbols, 1 layer, DMRSantenna ports #8 14 2 symbols, 1 layer, DMRS antenna ports #9 15 2symbols, 1 layer, DMRS antenna ports #10 16 2 symbols, 1 layer, DMRSantenna ports #11 17 2 symbols, 1 layer, DMRS antenna ports #12 18 1symbol, 2 layers, DMRS antenna ports #1~#2 19 1 symbol, 2 layers, DMRSantenna ports #3~#4 20 1 symbol, 2 layers, DMRS antenna ports #5~#6 21 2symbols, 2 layers, DMRS antenna ports #1~#2 22 2 symbols, 2 layers, DMRSantenna ports #3~#4 23 2 symbols, 2 layers, DMRS antenna ports #5~#6 242 symbols, 2 layers, DMRS antenna ports #7~#8 [[excluded]] 2 symbols, 2layers, DMRS antenna ports #9~#10 [[excluded]] 2 symbols, 2 layers, DMRSantenna ports #11~#12 25 1 symbol, 3 layers, DMRS antenna ports #1~#3 261 symbol, 3 layers, DMRS antenna ports #4~#6 27 2 symbols, 3 layers,DMRS antenna ports #1~#3 28 2 symbols, 3 layers, DMRS antenna ports#4~#6 29 2 symbols, 3 layers, DMRS antenna ports #7~#9 [[excluded]] 2symbols, 3 layers, DMRS antenna ports #10~#12 30 1 symbol, 4 layers,DMRS antenna ports #1~#4 31 2 symbols, 4 layers, DMRS antenna ports#1~#4

TABLE 67 Bit value Message 0 1 symbol, 1 layer, DMRS antenna ports #1 11 symbol, 1 layer, DMRS antenna ports #2 2 1 symbol, 1 layer, DMRSantenna ports #3 3 1 symbol, 1 layer, DMRS antenna ports #4 4 1 symbol,1 layer, DMRS antenna ports #5 5 1 symbol, 1 layer, DMRS antenna ports#6 6 2 symbols, 1 layer, DMRS antenna ports #1 7 2 symbols, 1 layer,DMRS antenna ports #2 8 2 symbols, 1 layer, DMRS antenna ports #3 9 2symbols, 1 layer, DMRS antenna ports #4 10 2 symbols, 1 layer, DMRSantenna ports #5 11 2 symbols, 1 layer, DMRS antenna ports #6 12 2symbols, 1 layer, DMRS antenna ports #7 13 2 symbols, 1 layer, DMRSantenna ports #8 14 2 symbols, 1 layer, DMRS antenna ports #9 15 2symbols, 1 layer, DMRS antenna ports #10 16 2 symbols, 1 layer, DMRSantenna ports #11 17 2 symbols, 1 layer, DMRS antenna ports #12 18 1symbol, 2 layers, DMRS antenna ports #1~#2 19 1 symbol, 2 layers, DMRSantenna ports #3~#4 20 1 symbol, 2 layers, DMRS antenna ports #5~#6 21 2symbols, 2 layers, DMRS antenna ports #1~#2 22 2 symbols, 2 layers, DMRSantenna ports #3~#4 23 2 symbols, 2 layers, DMRS antenna ports #5~#6 242 symbols, 2 layers, DMRS antenna ports #7~#8 25 2 symbols, 2 layers,DMRS antenna ports #9~#10 [[excluded]] 2 symbols, 2 layers, DMRS antennaports #11~#12 26 1 symbol, 3 layers, DMRS antenna ports #1~#3 27 1symbol, 3 layers, DMRS antenna ports #4~#6 28 2 symbols, 3 layers, DMRSantenna ports #1~#3 29 2 symbols, 3 layers, DMRS antenna ports #4~#6[[excluded]] 2 symbols, 3 layers, DMRS antenna ports #7~#9 [[excluded]]2 symbols, 3 layers, DMRS antenna ports #10~#12 30 1 symbol, 4 layers,DMRS antenna ports #1~#4 31 2 symbols, 4 layers, DMRS antenna ports#1~#4

TABLE 68 Bit value Message 0 1 symbol, 1 layer, DMRS antenna ports #1 11 symbol, 1 layer, DMRS antenna ports #2 2 1 symbol, 1 layer, DMRSantenna ports #3 3 1 symbol, 1 layer, DMRS antenna ports #4 4 1 symbol,1 layer, DMRS antenna ports #5 5 1 symbol, 1 layer, DMRS antenna ports#6 6 2 symbols, 1 layer, DMRS antenna ports #1 7 2 symbols, 1 layer,DMRS antenna ports #2 8 2 symbols, 1 layer, DMRS antenna ports #3 9 2symbols, 1 layer, DMRS antenna ports #4 10 2 symbols, 1 layer, DMRSantenna ports #5 11 2 symbols, 1 layer, DMRS antenna ports #6 12 2symbols, 1 layer, DMRS antenna ports #7 13 2 symbols, 1 layer, DMRSantenna ports #8 14 2 symbols, 1 layer, DMRS antenna ports #9 15 2symbols, 1 layer, DMRS antenna ports #10 16 2 symbols, 1 layer, DMRSantenna ports #11 17 2 symbols, 1 layer, DMRS antenna ports #12 18 1symbol, 2 layers, DMRS antenna ports #1~#2 19 1 symbol, 2 layers, DMRSantenna ports #3~#4 20 1 symbol, 2 layers, DMRS antenna ports #5~#6 21 2symbols, 2 layers, DMRS antenna ports #1~#2 22 2 symbols, 2 layers, DMRSantenna ports #3~#4 23 2 symbols, 2 layers, DMRS antenna ports #5~#6 242 symbols, 2 layers, DMRS antenna ports #7~#8 25 2 symbols, 2 layers,DMRS antenna ports #9~#10 26 2 symbols, 2 layers, DMRS antenna ports#11~#12 27 1 symbol, 3 layers, DMRS antenna ports #1~#3 [[excluded]] 1symbol, 3 layers, DMRS antenna ports #4~#6 28 2 symbols, 3 layers, DMRSantenna ports #1~#3 29 2 symbols, 3 layers, DMRS antenna ports #4~#6[[excluded]] 2 symbols, 3 layers, DMRS antenna ports #7~#9 [[excluded]]2 symbols, 3 layers, DMRS antenna ports #10~#12 30 1 symbol, 4 layers,DMRS antenna ports #1~#4 31 2 symbols, 4 layers, DMRS antenna ports#1~#4

FIG. 18 is a view showing a flowchart for illustrating a method oftransmitting and receiving a downlink DMRS according to the presentdisclosure.

In step S1810, the base station may indicate a downlink (DL) DMRSconfiguration type to the terminal by using high layer signaling. The DLDMRS configuration type may one of a DMRS configuration type 1 based onan IFDMA (or Comb) method and DMRS configuration type 2 based on a CDMgroup method.

In step S1820, the base station may indicate configuration informationof the DL DMRS to the terminal by using DCI. The configurationinformation of the DL DMRS may include information of a number ofsymbols, a number of layers, and an antenna port number of the DL DMRS.In addition, the above configuration information of the DL DMRS may beconfigured in a form of a signaling field having a 5-bit or 6-bit sizeand which is included in DCI described in the above various examples ofthe present disclosure. Accordingly, by indicating a specific bit valueto the terminal, the terminal may identify a number of symbols, a numberof layers, and an antenna port number of a DMRS corresponding to acorresponding bit value.

In step S1830, the base station may generate a DL DMRS based on the DLDMRS configuration type, and information of the number of symbols, thenumber of layers, and the antenna port number which are provided to theterminal.

In step S1840, the base station may transmit the generated DMRS bymapping on a physical resource.

In step S1850, the terminal may compare a DL DMRS received from the basestation with a DMRS generated by the terminal based on the DL DMRSconfiguration type and the DL DMRS configuration information receivedfrom the base station in steps S610 and S1820, and estimate a DLchannel. In other words, by comparing a DMRS that is estimated to havebeen originally transmitted from the base station with a DMRS distortedby passing a DL channel, the DL channel may be estimated.

FIG. 19 is a view showing a flowchart for illustrating a method oftransmitting and receiving an uplink DMRS according to the presentdisclosure.

In step S1910, the base station may indicate an uplink (UL) DMRSconfiguration type to the terminal by using high layer signaling. The ULDMRS configuration type may be one of a DMRS configuration type 1 basedon an IFDMA (or Comb) method and a DMRS configuration type 2 based on aCDM group method.

In step S1920, the base station may indicate to the terminalconfiguration information of the DMRS. The configuration information ofthe UL DMRS may include information of a number of symbols, a number oflayers, and an antenna port number of the UL DMRS. In addition, theabove configuration information of the UL DMRS may be configured in aform of a signaling field having a 5 bit or a 6-bit size which isincluded in DCI described in above various examples of the presentdisclosure. Accordingly, by indicating a specific bit value to theterminal, the terminal may identify a number of symbols, a number oflayers, and an antenna port number of a DMRS corresponding to acorresponding bit value.

In step S1930, the terminal may generate a UL DMRS based on the UL DMRSconfiguration type, and the information of the number of symbols, thenumber of layers, and the antenna port number which are received fromthe base station.

In step S1940, the terminal may transmit the generated DMRS by mappingon a physical resource.

In step S1950, the base station may compare a UL DMRS received from theterminal with a DMRS generated by the base station based on the UL DMRSconfiguration type and the UL DMRS configuration information which areprovided to the terminal in steps S1910 and S1920, and estimate a ULchannel. In other words, by comparing a DMRS that is estimated to havebeen originally transmitted from the terminal with a DMRS distorted bypassing a UL channel, the UL channel may be estimated.

FIG. 20 is a view showing a configuration of a wireless device accordingto the present disclosure.

A DMRS configuration information transmitting unit 2016 may configure asignaling field having a 5-bit or a 6-bit size and which indicates anumber of symbols, a number of layers, and an antenna port number of aDL/UL DMRS, and transmit the generated signaling field to a terminaldevice 2050 by including the same in a downlink control information(DCI) format through a transceiver 2030.

A DMRS transmitting receiving unit 2017 may transmit to the terminaldevice 2050 the DL DMRS by mapping on a physical resource through thetransceiver 2030 based on a DMRS configuration type of the DL DMRS andDMRS configuration information. In addition, a DMRS transmittingreceiving unit 2017 may receive, through the transceiver 2030, on aphysical resource a UL DMRS transmitted from the terminal device 2050and which is determined based on the DMRS configuration type and theDMRS configuration information of the UL DMRS.

A channel estimating unit 2018 may estimate a UL channel by comparing aUL DMRS received from the terminal device 2050 with a DMRS generated bya base station device 2000.

A DMRS configuration identifying unit 2062 may identify a number ofsymbols, a number of layers, and an antenna port number of a DMRSreceived from the base station device 2000 by using DCI based oninformation of the DMRS configuration type for the downlink or uplink(DL/UL) DMRS received from the base station device 2000 by using highlayer signaling.

A physical layer processing unit 2065 of a processor 2060 of theterminal device 2050 may include a DL/UL DMRS configuration informationreceiving unit 2066, a DMRS transmitting receiving unit 2067, and achannel estimating unit 2068.

The DMRS configuration information receiving unit 2066 may receive DCIfrom the base station device 2000 through a physical downlink controlchannel (PDCCH), etc. In addition, a number of symbols, a number oflayers, and an antenna port number of a DL/UL DMRS may be checked, thenumber of symbols, the number of layers, and the antenna port number ofa DL/UL DMRS are indicated by a bit value of a signaling field having a5-bit or 6-bit size and which is included in the received DCI.

The DMRS transmitting receiving unit 2067 may transmit to the basestation device 2000 a UL DMRS by mapping on a physical resource throughthe transceiver 2030 based on the DMRS configuration type and the DMRSconfiguration information of the UL DMRS. In addition, the DMRStransmitting receiving unit 2067 may receive, through the transceiver2030, a DL DMRS transmitted from the base station device 2000 on aphysical resource that is determined based on the DMRS configurationtype and the DMRS configuration information of the DL DMRS.

The channel estimating unit 2068 may estimate a DL channel by comparinga DL DMRS received from the base station device 2000 with a DMRSgenerated by the terminal device 2050.

The present invention relates to a method of indicating a demodulationreference signal (DMRS) layers, antenna ports, and information ofrate-matching for a new wireless communication system, and an apparatusthereof.

In the international telecommunication union (ITU), development for aninternational mobile telecommunication (IMT) framework and standard hasbeen conducted. Recently, discussions are underway for 5G communicationthrough a program called “IMT for 2020 and beyond”.

In order to satisfy the requirement of the “IMT for 2020 and beyond”, anew radio (NR) system of a third generation partnership projectdiscloses a method of supporting various subcarrier spacing (SCS) inconsideration with various scenarios, service requirements, andpotential system compatibility. In addition, in order to overcome badenvironment conditions such as high path-loss, phase-noise, frequencyoffset, etc. occurring at a high carrier frequency, the NR systemconsiders a transmission of a physical signal/channel by using aplurality of beams. However, according to various SCS supported in theNR system, a method of configuring a reference signal in considerationwith a transmission using a plurality of beams, and transmitting andreceiving the same is not determined in detail yet.

Accordingly, an object of the present invention is to provide a methodof indicating a DMRS layer, an antenna port, and rate-matching, and anapparatus thereof, wherein the method and apparatus efficientlyconfigures and indicates a layer and an antenna port in associationtherewith which are associated with operations of a single-user multipleinput multiple output (SU-MIMO) and a multi-user MIMO (MU-MIMO).

Another object of the present invention is to provide a method ofindicating a DMRS layer, an antenna port, and rate-matching, and anapparatus thereof, wherein the method and apparatus is capable ofpreventing wrong decoding between a DMRS and data.

Still another object of the present invention is to provide a method ofindicating a DMRS layer, an antenna port, and rate-matching, and anapparatus thereof, wherein the method and apparatus is capable ofreducing signaling overhead.

According to an aspect of the present invention, a method oftransmitting a DMRS, wherein the method transmits a demodulationreference signal (DMRS) from a wireless communication system to aterminal, the method includes: determining a DMRS configuration type ofa DMRS to be transmitted to the terminal among a plurality of DMRSconfiguration types; transmitting to the terminal information of thedetermined DMRS configuration type by using high layer signaling;determining a number layers, an antenna port number, a number ofsymbols, and a code division multiplexing (CDM) group according to anMU-MIMO of the DMRS to be transmitted to the terminal within thedetermined DMRS configuration type, and transmitting the determinedinformation to the terminal; and configuring the DMRS according to thedetermined information and transmitting the configured DMRS to theterminal.

According to the present invention, for a DMRS used for demodulating adata channel, a layer and an antenna port in association therewith canbe efficiently configured and indicated in consideration with operationsof a SU-MIMO and an MU-MIMO.

In addition, according to the present invention, a symbol transmittedthrough a DMRS and whether or not data is multiplexed by using a FDMmethod may be obtained by rate-matching information, thus wrong decodingbetween a DMRS and data can be prevented.

In addition, according to the present invention, when indicating aco-scheduled code division multiplexing (CDM) group for rate-matching,rather than indicating all co-scheduled CDM groups, information definedaccording to a specific rule is indicated, thus signaling overhead canbe reduced.

Hereinafter, in the present description, some exemplary embodiments ofthe present invention will be described in detail with reference to theaccompanying drawings. In the following description, the same elementswill be designated by the same reference numerals although they areshown in different drawings. Further, in the following description ofthe present disclosure, a detailed description of known functions andconfigurations incorporated herein will be omitted when it may make thesubject matter of the present disclosure rather unclear.

In addition, the present description is based with respect to a wirelesscommunication network, operations performed in the wirelesscommunication network may be performed during controlling the network,and transmitting data by a system managing the corresponding wirelesscommunication network (for example base station), or may be performed ina terminal included in the corresponding wireless communication network.

FIG. 21 is a view showing a wireless communication system to which thepresent invention is applied.

A network configuration shown in FIG. 21 may be a network configurationof a new radio (NR) system. Hereinafter, the wireless communicationsystem to which the present invention is applied is referred to an NRsystem. The NR system may include a network configuration satisfying thestandard of “International Mobile Telecommunication (IMT)-2020 andbeyond” defined in an international telecommunication union—radiocommunication (ITU-R) sector.

Referring to FIG. 21, in an NR system 10, a base station (BS) 11 and auser equipment (UE: Terminal) 12 may transmit and receive data in awireless manner.

In the NR system 10, the base station 11 may provide communicationservice to the terminal present within a coverage through a specificfrequency domain. It may be represented as a term of a site servicedunder the coverage of the base station. The site may include a pluralityof areas 15 a, 15 b, and 15 c which is called a sector. Each sectorincluded in the site may be identified based on an identifier differentfrom each other. Each of the sectors 15 a, 15 b, and 15 c may beunderstood as a partial area covered by the base station 11.

The base station 11 refers to a station that generally communicates withthe terminal 12, and may be called such as eNodeB (evolved-NodeB, eNB),gNodeB (gNB), base transceiver system (BTS), access point, femto basestation (Femto eNodeB, Femto gNodeB), home base station (HeNodeB: HomeeNodeB, Home gNodeB), relay, remote radio head (RRH), etc.

In addition, the base station 11 may be referred to by various termsaccording to a coverage size provided by the corresponding base stationsuch as mega cell, macro cell, micro cell, pico cell, femto cell, etc.The cell may be used as a frequency domain provided by the base station,a coverage of the base station, or a term of indicating the base station

The terminal 12 may be fixed or may move, and may be called a mobilestation (MS), mobile terminal (MT), user terminal (UT), subscriberstation (SS), wireless device, personal digital assistant (PDA),wireless modem, handheld device, etc.

Hereinafter, a downlink means communicating or a communicating path fromthe base station 11 to the terminal 12, and an uplink meanscommunicating or a communicating path from terminal 12 to the basestation 11. In the downlink, a transmitter may be a part of the basestation 11, and a receiver may be a part of the terminal 12. In theuplink, a transmitter may be a part of the terminal 12 and a receivermay be a part of the base station 11.

Meanwhile, there is no limit for a multiple access method applied to thewireless communication system 10. For example, various multiple accessmethods such as code division multiplexing (CDM), code division multipleaccess (CDMA), time division multiple access (TDMA), interleaved FDMA(IFDMA), frequency division multiple access (FDMA), orthogonal frequencydivision multiple access (OFDMA), single carrier-FDMA (SC-FDMA),OFDM-FDMA, OFDM-TDMA, OFDM-CDMA, etc. may be used. In addition, in anuplink transmission and downlink transmission, a time division duplex(TDD) method of transmitting by using times different from each other ora frequency division duplex (FDD) method of transmitting by usingfrequencies different from each other may be used.

Hereinafter, a numerology in consideration with the NR system will bedescribed. A numerology may mean a general element or a numerical valueof a factor which generates a resource grid on a time-frequency domainfor designing a system. For example, as an example of numerology of a3GPP LTE/LTE-A system, subcarrier spacing (SCS) corresponds to 15 kHz(or to 7.5 kHz in case of a multicast-broadcast single-frequency network(MBSFN)). However, the term of the numerology may not mean be arestrictive meaning for SCS, and may mean including a cyclic prefix (CP)length, a transmit time interval (TTI) length, a number of orthogonalfrequency division multiplexing (OFDM) symbols within a predeterminedtime section, a duration of one OFDM symbol, etc. which are determinedbased on an associative relation with SCS or based on SCS. In otherwords, a numerology different from each other may be classified byvalues differing in at least one of SCS, a CP length, a TTI length, anumber of OFDM symbols within a predetermined time section, and aduration of one OFDM symbol.

In order to satisfy requirements presented in “IMT for 2020 and beyond”,the NR system considers a plurality of numerologies for variousscenarios, various service requirements, compatibility with potentialnew systems, etc. In detail, in a numerology of the present wirelesscommunication system, it is difficult to support higher frequencydomain, faster moving speed, lower delay, etc. than requested by “IMTfor 2020 and beyond, thus defining a new numerology is required.

For example, the NR system may support an application such as enhancedmobile broadband (eMBB), massive machine type communications(mMTC)/ultra machine type communications (uMTC), ultra-reliable and lowlatency communications (URLLC), etc. Particularly, in URLLC or eMBBservice, requirement for a user plane latency is 0.5 ms for an uplinkand 4 ms for an uplink/downlink, and this means that a reduction of asignificant latency is required than the latency requirement of a 3GPPlong term evolution (LTE) and LTE-advanced (LTE-A) system which is 10ms.

In order to satisfy various scenarios and various requirements describedabove in one NR system, supporting of various numerologies is required.Particularly, in a conventional LTE/LTE-A system, different fromsupporting one SCS, supporting of a plurality of SCS is required.

In order to solve a problem in that a wide bandwidth is not used in aconventional frequency range or carrier such as 700 MHz or 2 GHz, a newnumerology for an NR system supporting a plurality of SCSs may bedetermined by assuming a wireless communication system operating in afrequency range or carrier such as 3 GHz or lower, 3 GHz-6 GHz, or 6GHZ-52.6 GHz, but a range of the present disclosure is not limitedthereto.

In the NR system, one radio frame may correspond to 10 ms on a temporalaxis, and one subframe may correspond to 1 ms on a temporal axis. Inaddition, one slot may correspond to fourteen or seven symbols on atemporal axis. Accordingly, a number of available slots and symbolsaccording to a subcarrier spacing (SCS) respectively in considerationwithin one radio frame corresponding to 10 ms is as Table 1 below. InTable 69, an SCS of 480 KHz may not be considered.

TABLE 69 Number of slots Number of slots Number of within 10 ms within10 ms symbols (fourteen symbols (seven symbols within SCS in one slot)in one slot) 10 ms  15 KHz 10 20 140  30 KHz 20 40 280  60 KHz 40 80 560120 KHz 80 N/A 1120 240 KHz 160 N/A 2240 480 KHz 320 N/A 4480

One physical resource block (PRB) may be defined as a resource areacorresponding to one slot on a temporal axis, and twelve subcarriers ona frequency axis.

In the above NR system, a demodulation reference signal (DMRS) fordemodulating a specific physical channel is required. For example, aDMRS for demodulating a physical data channel, a DMRS for demodulating aphysical control channel, etc. may be defined in the NR system.

In detail, in the NR system, up to eight layers may be supported fortransmitting a single-user multiple input multiple output (SU-MIMO), andup to twelve orthogonal layers may be supported for transmitting amulti-user MIMO (MU-MIMO). The above layers may be mapped to an antennaport (in other words, logical antenna), and transmitted through aphysical channel. Herein, in order to correctly demodulate a signaltransmitted through each layer of a physical channel or an antenna port,a reference signal (RS) of a corresponding layer or antenna is required,and the RE may be defined as a DMRS.

In the NR system, a number of DMRS orthogonal antenna ports(hereinafter, DMRS antenna port) may be up to twelve. For example, aDMRS antenna port number (antenna port number) may be defined as from #0to #11.

In an MU-MIMO, up to twelve layers being classified from each other maybe supported across all terminals. For example, in an MU-MIMO, eachlayer used by each terminal may be one of DMRS antenna port numbers #0,#1, #2, #3, #4, #5, #6, #7, #8, #9, #10, and #11. However, an actualDMRS antenna port number may vary according to an RS antenna port numbercorresponding to a first antenna port of a DMRS. When an RS antenna portnumber corresponding to the first RS antenna port of the DMRS is #A, thetwelve DMRS antenna port numbers may be assigned as #A, #A+1, #A+2,#A+3, #A+4, #A+5, #A+6, #A+7, #A+8, #A+9, #A+10, and #A+11.

Meanwhile, a DMRS pattern may mean which DMRS configuration is used foran uplink and downlink, and may be classified into four types accordingto a number of symbols used for the DMRS.

1. When a first DMRS configuration type based on an IFDMA is applied,and one symbol is used for a DMRS.

2. When a first DMRS configuration type based on an IFDMA is applied,and two symbols are used for a DMRS.

3. When a second DMRS configuration type based on a CDM is applied, andone symbol is used for a DMRS.

4. When a second DMRS configuration type based on a CDM is applied, andtwo symbols are used for a DMRS.

In addition, a maximum number of available DMRS layers for each terminalmay be defined as below for a case of a SU-MIMO and for a case of anMU-MIMO.

In case of a SU-MIMO, when a first DMRS configuration type is appliedand one symbol is used for a DMRS, up to four layers being classifiedfrom each other may be supported to a terminal. When a first DMRSconfiguration type is applied and two symbols are used for a DMRS, up toeight layers being classified from each other may be supported to aterminal. In addition, when a DMRS configuration type 2 is applied andone symbol is used for a DMRS, up to six layers being classified fromeach other may be supported to a terminal. When a DMRS configurationtype 2 is applied and two symbols are used for a DMRS, up to eightlayers being classified from each other may be supported to a terminal.

In case of an MU-MIMO, when a first DMRS configuration type is appliedand one symbol is used for a DMRS, up to two layers being classifiedfrom each other may be supported to each terminal. When a first DMRSconfiguration type is applied and two symbols are used for a DMRS, up tofour layers being classified from each other may be supported to eachterminal. When a DMRS configuration type 2 is applied and one symbol isused for a DMRS, up to four layers being classified from each other maybe supported to each terminal. When a DMRS configuration type 2 isapplied and two symbols are used for a DMRS, up to four layers beingclassified from each other may be also supported to each terminal.

When a maximum number of available layers for each terminal is N, eachlayer may correspond to any one of DMRS antenna port numbers #0, #1, #2,#3, #4, #5, #6, #7, #8, #9, #10, and #11.

Hereinafter, a DMRS pattern for the NR system will be described indetail with accompanied drawings.

FIG. 22 is a view showing a DMRS pattern when a first DMRS configurationtype is applied and one symbol is used for a DMRS.

In FIG. 22, a “Comb pattern A” and a “Comb pattern B” in one symbol andtwelve subcarriers (corresponding to one PRB in a frequency domain) arerepresented. A DMRS pattern shown in FIG. 22 may extend, in a frequencyaxis, by being repeated to a plurality of PRBs by a bandwidth assignedfor transmitting to a physical channel (for example, physical downlinkshared channel (PDSCH), physical uplink shared channel (PUSCH), etc.) ofeach terminal. In addition, in a temporal axis, the DMRS pattern may beapplied to each DMRS configuration (front-loaded DMRS configuration oradditional DMRS configuration) within one slot. The “Comb pattern A” maybe defined as a DMRS pattern applied to an even numbered subcarrier, andthe “Comb pattern B” may be defined as a DMRS pattern applied to an oddnumbered subcarrier.

As shown in FIG. 22, for one symbol within one PRB, six resourceelements (RE) may be assigned to each Comb pattern. Herein, a DMRSantenna port configuration may be as Table 70 below.

TABLE 70 Comb pattern CS(Cyclic Shift) DMRS antenna port #0 Comb patternA CS value A DMRS antenna port #1 Comb pattern A CS value B DMRS antennaport #2 Comb pattern B CS value A DMRS antenna port #3 Comb pattern B CSvalue B

In Table 70, a Comb pattern is the “Comb pattern A” or the “Comb patternB” shown in FIG. 22, a cyclic shift (CS) is a cyclic delay value of aDMRS sequence. When a range of available values is from 0 to X, the “CSvalue A” may have a value of 0, and the “CS value B” may have a value ofX/2. For example, when X=12, the “CS value A” may have a value of 0, andthe “CS value B” may have a value of 6. When X=2π, the “CS value A” mayhave a value of 0, and the “CS value B” may have a value of π, but it isnot limited thereto.

Referring to Table 70, DMRS antenna port numbers may be preferentiallyclassified into CS values, and then classified into Comb patterns. AComb pattern A may be applied to DMRS antenna port numbers #0 and #1,and a Comb pattern B may be applied to DMRS antenna ports #2 and #3.

FIG. 23 is a view showing a DMRS pattern when a first DMRS configurationtype is applied and two symbols are used for a DMRS.

In FIG. 23, a “Comb pattern A” and a “Comb pattern B” in two symbols andtwelve subcarriers (corresponding to one PRB in a frequency domain) arerepresented. A DMRS pattern shown in FIG. 23 may expand, in a frequencyaxis, by being repeated up to a plurality of PRBs by a bandwidthassigned for transmitting a physical channel (for example, PDSCH, PUSCH,etc.) for each terminal. In addition, in a temporal axis, the DMRSpattern may be applied to each DMRS configuration (front-loaded DMRSconfiguration or additional DMRS configuration) within one slot.

As shown in FIG. 23, for one symbol within one PRB, six REs may beassigned for each Comb pattern. Herein, a DMRS antenna portconfiguration may be as Table 71 below.

TABLE 71 Comb pattern CS(Cyclic Shift) TD-OCC DMRS antenna Comb patternA CS value A [+1, +1] port #0 DMRS antenna Comb pattern A CS value B[+1, +1] port #1 DMRS antenna Comb pattern B CS value A [+1, +1] port #2DMRS antenna Comb pattern B CS value B [+1, +1] port #3 DMRS antennaComb pattern A CS value A [+1, −1] port #4 DMRS antenna Comb pattern ACS value B [+1, −1] port #5 DMRS antenna Comb pattern B CS value A [+1,−1] port #6 DMRS antenna Comb pattern B CS value B [+1, −1] port #7

In Table 71, a Comb pattern is the “Comb pattern A” or the “Comb patternB” shown in FIG. 23. A CS is a cyclic delay value of a DMRS sequence.When a range of available values is from 0 to X, the “CS value A” mayhave a value of 0, and the “CS value B” may have a value of X/2. Forexample, when X=12, the “CS value A” may have a value of 0, and the “CSvalue B” may have a value of 6. When X=2π, the “CS value A” may have avalue of 0, and the “CS value B” may have a value of π, but it is notlimited thereto.

In addition, a time domain-orthogonal cover code (TD-OCC) may be appliedto two REs that are adjacent in a temporal axis on the same subcarrierwithin each Comb pattern. A value thereof is [+1, +1] or [+1, −1] for[RE with a temporal axial precedence on the same subcarrier, REfollowing in a temporal axis on the same subcarrier]. When generating aDMRS sequence, ‘+1’ or ‘−1’ may be multiplied by a sequence value of aDMRS sequence mapped to a corresponding RE.

Referring to Table 71, DMRS antenna port numbers may be preferentiallyclassified into CS value, then classified into Comb patterns, andlastly, classified into TD-OCCs. A Comb pattern A may be applied to DMRSantenna port numbers #0, #1, #4, and #5, and a Comb pattern B may beapplied to DMRS antenna port numbers #2, #3, #6, and #7.

FIG. 24 is a view showing a DMRS pattern when a second DMRSconfiguration type is applied and one symbol is used for a DMRS.

In FIG. 24, a “CDM group A”, a “CDM group B”, and a “CDM group C” in onesymbol and twelve subcarriers (corresponding to one PRB in a frequencydomain) are represented. A DMRS pattern shown in FIG. 24 may expand, ina frequency axis, by being repeated to a plurality of PRBS by abandwidth assigned for transmitting a physical channel (for example,PDSCH, PUSCH, etc.) of each terminal. In addition, in a temporal axis,the DMRS pattern may be applied to each DMRS configuration (front-loadedDMRS configuration or additional DMRS configuration) within one slot.

As shown in FIG. 24, for one symbol within one PRB, four REs may beassigned for each CDM group. Herein, a DMRS antenna port configurationmay be as Table 72 below.

TABLE 72 CDM group FD-OCC DMRS antenna port #0 CDM group A [+1, +1] DMRSantenna port #1 CDM group A [+1, −1] DMRS antenna port #2 CDM group B[+1, +1] DMRS antenna port #3 CDM group B [+1, −1] DMRS antenna port #4CDM group C [+1, +1] DMRS antenna port #5 CDM group C [+1, −1]

In Table 72, a CDM group is the “CDM group A”, the “CDM group B”, or the“CDM group C” shown in FIG. 23. A frequency domain-orthogonal cover code(FD-OCC) may be applied to two REs that are adjacent in a frequency axison the same symbol within each CDM group. A value thereof is [+1, +1] or[+1, −1] for [RE with a frequency axial precedence on the same symbol,RE following in a frequency axis on the same symbol]. When generating aDMRS sequence, ‘+1’ or ‘−1’ may be multiplied by a sequence value of aDMRS sequence mapped to a corresponding RE.

Referring to Table 72, DMRS antenna port numbers may be preferentiallyclassified into FD-OCCs, and then classified into CDM groups. A CDMgroup A may be applied to DMRS antenna port numbers #0 and #1, a CDMgroup B may be applied to DMRS antenna port numbers #2 and #3, and a CMDgroup C may be applied to DMRS antenna port numbers #4 and #5.

FIG. 25 is a view showing a DMRS pattern when a second DMRSconfiguration type is applied and two symbols are used for a DMRS.

In FIG. 25, a “CDM group A”, a “CDM group B”, and a “CDM group C” in twosymbols and twelve subcarriers (corresponding to one PRB in a frequencydomain) are represented. A DMRS pattern shown in FIG. 25 may expand, ina frequency axis, by being repeated to a plurality of PRBs by abandwidth assigned for transmitting to a physical channel (for example,PDSCH, PUSCH, etc.) of each terminal. In addition, in a temporal axis,the DMRS pattern may be applied to each DMRS configuration (front-loadedDMRS configuration or additional DMRS configuration) within one slot. Asshown in FIG. 25, for one symbol within one PRB, four REs may beassigned for each CDM group. Herein, a DMRS antenna port configurationmay be as Table 73 below.

TABLE 73 CDM group FD-OCC TD-OCC DMRS antenna port #0 CDM group A [+1,+1] [+1, +1] DMRS antenna port #1 CDM group A [+1, −1] [+1, +1] DMRSantenna port #2 CDM group B [+1, +1] [+1, +1] DMRS antenna port #3 CDMgroup B [+1, −1] [+1, +1] DMRS antenna port #4 CDM group C [+1, +1] [+1,+1] DMRS antenna port #5 CDM group C [+1, −1] [+1, +1] DMRS antenna port#6 CDM group A [+1, +1] [+1, −1] DMRS antenna port #7 CDM group A [+1,−1] [+1, −1] DMRS antenna port #8 CDM group B [+1, +1] [+1, −1] DMRSantenna port #9 CDM group B [+1, −1] [+1, −1] DMRS antenna port #10 CDMgroup C [+1, +1] [+1, −1] DMRS antenna port #11 CDM group C [+1, −1][+1, −1]

In Table 73, a CDM group is the “CDM group A”, the “CDM group B”, or the“CDM group C” shown in FIG. 24. A FD-OCC may be applied to two REs thatare adjacent in a frequency axis on the same symbol within each CDMgroup. A value thereof is [+1, +1] or [+1, −1] for [RE with a frequencyaxial precedence on the same symbol, RE following in a frequency axis onthe same symbol]. When generating a DMRS sequence, ‘+1’ or ‘−1’ may bemultiplied by a sequence value of a DMRS sequence mapped to acorresponding RE. In addition, a TD-OCC may be applied to two REs thatare adjacent in a temporal axis on the same subcarrier. A value thereofis [+1, +1] or [+1, −1] for [RE with a temporal axial precedence on thesame subcarrier, RE following in a temporal axis on the samesubcarrier]. When generating a DMRS sequence, ‘+1’ or ‘−1’ may bemultiplied by a sequence value of a DMRS sequence mapped to acorresponding RE.

Referring to Table 73, DMRS antenna port numbers may be preferentiallyclassified into FD-OCCs, then classified into CDM groups, and lastlyclassified into TD-OCC values. A CDM group A may be applied to DMRSantenna ports #0, #1, #6, and #7, a CDM group B may be applied to DMRSantenna ports #2, #3, #8, and #9, and a CDM group C may be applied toDMRS antenna ports #4, #5, #10, and #11.

FIG. 26 is a view showing a mapping example of an OCC applied to thepresent invention.

In FIG. 26, detailed examples in which a “TD-OCC” of FIG. 22 and Table23, a “FD-OCC” of FIG. 23 and Table 4, and “FD-OCC and TD-OCC” of FIG.24 and Table 73 are mapped to DMRS REs are represented.

Referring to FIG. 26, when a TD-OCC has a value of [+1, +1] for two REscorresponding to two consecutive symbols on the same subcarrier, a DMRSsequence value mapped to an RE with a low symbol index may be multipliedby +1, and a DMRS sequence value mapped to an RE of a next symbol indexmay be multiplied by +1.

When a TD-OCC has a value of [+1, −1] for two REs corresponding to twoconsecutive subcarriers on the same symbol, a DMRS sequence value mappedto an RE with a low subcarrier index may be multiplied by +1, and a DMRSsequence value mapped to an RE of a next subcarrier index may bemultiplied by −1.

When a FD-OCC has a value of [+1, +1] for two REs corresponding to twoconsecutive subcarriers on the same symbol, a DMRS sequence value mappedto an RE with a low subcarrier index may be multiplied by +1, and a DMRSsequence value mapped to an RE of a next subcarrier index may bemultiplied by +1.

When a FD-OCC has a value of [+1, −1] for two REs corresponding toconsecutive two subcarriers on the same symbol, a DMRS sequence valuemapped to an RE with a low subcarrier index may be multiplied by +1, anda DMRS sequence value mapped to an RE of a next subcarrier index may bemultiplied by −1.

When a TD-ODD and a FD-OCC are all applied, for RES belonging to thesame CDM group, an OCC value may be multiplied in a temporal axis and afrequency axis according to the above described method.

Hereinafter, for a DMRS used for demodulating a data channel in the NRsystem, a method of configuring a layer and an antenna port fortransmitting a DMRS, and a signaling method for indicating the same willbe described in consideration of the following factors.

In the NR system, a DMRS may be configured in a first DMRS configurationtype based on an IFDMA or may be configured in a second DMRSconfiguration type based on a CDM.

In addition, each DMRS configuration may be configured with one symbolor two symbols. Accordingly, the DMRS configuration may be classifiedinto: (1) a first DMRS configuration type using one symbol; (2) a firstDMRS configuration type using two symbols; (3) a second DMRSconfiguration type using one symbol; and (4) a second DMRS configurationtype using two symbols.

In case of a SU-MIMO, for (1) a first DMRS configuration type using onesymbol, (2) a first DMRS configuration type using two symbols. (3) asecond DMRS configuration type using one symbol, and (4) a second DMRSconfiguration type using two symbols, up to four, eight, six, and eightlayers (and the quantity of antenna ports corresponding to the quantityof layers) may be respectively classified.

In case of an MU-MIMO, for (1) a first DMRS configuration type using onesymbol, (2) a first DMRS configuration type using two symbols. (3) asecond DMRS configuration type using one symbol, and (4) a second DMRSconfiguration type using two symbols, up to two, four, four, and fourlayers (and the quantity of antenna ports corresponding to the quantityof layers) may be respectively classified. In addition, in an MU-MIMO,up to twelve layers (and the quantity of antenna ports corresponding tothe quantity of layers) may be classified for all terminalscommunicating with a base station.

In addition, in the NR system, for rate-matching purposes, whenindicating a CDM group used by a specific terminal, a CDM group used byanother terminal (hereinafter, a co-scheduled CDM group) may beindicated as well. However, when indicating the co-scheduled CDM group,in order to reduce signaling overhead, information defined according toa specific rule may be indicated rather than indicating all co-scheduledCDM groups.

Hereinafter, indicating a co-scheduled CDM group for rate-matching willbe described in detail.

An RE pattern for each DMRS configuration shown in FIGS. 22 to 25 may beorganized as below.

When one symbol is used in a first DMRS configuration pattern based onan IFDMA, a Comb pattern A may be applied to DMRS antenna ports #0 and#1, and a Comb pattern B may be applied to DMRS antenna ports #2 and #3.

When two symbols are used in a first DMRS configuration pattern based onan IFDMA, a Comb pattern A may be applied to DMRS antenna ports #0, #1,#4, and #5, and a Comb pattern B may be applied to DMRS antenna ports#2, #3, #6, and #7.

A Comb pattern group may be configured with antenna ports using the sameRE pattern. Antenna ports within a Comb pattern group may share the sameRE resources and may be classified into CS values or FD-OCCs or both.The Comb pattern group may be defined as a CDM group as similar to asecond DMRS configuration type.

When one symbol is used in a second DMRS configuration pattern based ona CDM, a CDM group A may be applied to DMRS antenna ports #0 and #1, aCDM group B may be applied to DMRS antenna ports #2 and #3, and a CDMgroup B may be applied to DMRS antenna ports #4 and #5.

When two symbols are used in a second DMRS configuration pattern basedon a CDM, a CDM group A may be applied to DMRS antenna ports #0, #1, #6,and #7, a CDM group B may be applied to DMRS antenna ports #2, #3, #8,and #9, and a CDM group C may be applied to DMRS antenna ports #4, #5,#10, and #11.

A CDM group may be configured with antenna ports using the same REpattern. Antenna ports within a CDM group may share the same REresources and may be classified into FD-OCCs or TD-OCCs or both.

A DMRS and data (NR-PDSCH or NR-PUSCH) may be multiplexed in a FDMwithin the same symbol. However, in an MU-MIMO environment, when aspecific terminal transmits a DMRS by using a RE pattern correspondingto a first CDM group, the specific terminal may not obtain informationwhether or not a RE pattern corresponding to remaining CDM groups,except for the first CDM group, is used by other terminals. Accordingly,in the above case, when performing rate-matching for a datatransmission, it is not possible to obtain information of whether toinclude or to exclude an RE pattern corresponding to the remaining CDMgroups. When it is assumed that the RE pattern corresponding to theremaining CDM groups is always excluded from a data transmission, the REpattern belonging to the remaining CDM group is excluded in a datatransmission even though other terminals do not transmit a DMRS, thuswireless resource waste may occur and accordingly, performancedegradation also may occur. When it is assumed that the RE patterncorresponding to the remaining CDM group is included in a datatransmission, the RE pattern corresponding to the remaining CDM group isincluded in a data transmission when other terminals transmit a DMRS,and it becomes difficult to correctly demodulate data. In addition, thisalso may cause performance degradation. Accordingly, in order to solvethe above problems, the base station may indicate a co-scheduled CDMgroup used by another terminal for rate-matching when the base stationindicates a CDM group for a DMRS to a specific terminal. All cases ofindicating the co-scheduled CDM group are represented as Table 74 below.

TABLE 74 Co-scheduled CDM DMRS CDM group used by group used by Caseconfiguration specific terminal other terminal Case 1 Configuration Combpattern A None Case 2 type 1 Comb pattern A Comb pattern B Case 3 Combpattern B None Case 4 Comb pattern B Comb pattern A Case 5 Comb patternA, B No need for indication Case 6 Configuration CDM group A None Case 7type 2 CDM group A CDM group B Case 8 CDM group A CDM group C Case 9 CDMgroup A CDM group B, C Case 10 CDM group B None Case 11 CDM group B CDMgroup A Case 12 CDM group B CDM group C Case 13 CDM group B CDM group A,C Case 14 CDM group C None Case 15 CDM group C CDM group A Case 16 CDMgroup C CDM group B Case 17 CDM group C CDM group A, B Case 18 CDM groupA, B None Case 19 CDM group A, B CDM group C Case 20 CDM group A, C NoneCase 21 CDM group A, C CDM group B Case 22 CDM group B, C None Case 23CDM group B, C CDM group A Case 24 CDM group A, B, C No need forindication

As Table 74, when all cases of indicating a co-scheduled CDM group forrate-matching are considered, signaling overhead becomes worse sincethere are lots of cases. Accordingly, in order to reduce signalingoverhead, rather than indicating all cases of the co-scheduled CDMgroup, it is possible to specify certain cases according to a specificrule and to indicate the specified cases.

Examples of the specific rule are as below.

1. In case of a DMRS configuration using one symbol in a first DMRSconfiguration type, when a total number of antenna ports inconsideration with an MU-MIMO is N, and N is ‘1’ or ‘2’, a Comb patternA is used. When N is ‘3’ or ‘4’, a Comb pattern A and a Comb pattern Bare used.

2. In case of a DMRS configuration using two symbols in a first DMRSconfiguration type, when a total number of antenna ports inconsideration with an MU-MIMO is N and N is any one of ‘1’ to ‘4’, aComb pattern A is used. When N is any one of ‘5’ to ‘8’, a Comb patternA and a Comb pattern B are used.

3. In case of a DMRS configuration using one symbol in a second DMRSconfiguration type, when a total number of antenna ports inconsideration with an MU-MIMO is N and N is ‘1’ or ‘2’, a CDM group A isused. When N is ‘3’ or ‘4’, a CDM group A and a CDM group B are used.When N is ‘5’ or ‘6’, a CDM group A, a CDM group B, and a CDM group Care used.

4. In case of a DMRS configuration using two symbols in a second DMRSconfiguration type 2, when a total number of antenna ports inconsideration with an MU-MIMO is N and N is any one of ‘1’ to ‘4’, a CDMgroup A is used. When N is any one of ‘5’ to ‘8’, a CDM group A and aCDM group B are used. When N is any one of ‘9’ to ‘12’, a CDM group A, aCDM group B, and a CDM group C are used.

In other words, in case of a first DMRS configuration type, for a totalnumber N of antenna ports used for a plurality of terminals in anMU-MIMO, N antenna ports may be assigned to a Comb pattern A, and thenassigned to a Comb pattern B.

In addition, in case of a second DMRS configuration type, for a totalnumber N of antenna ports used for a plurality of terminals in anMU-MIMO, N antenna ports may be assigned to a CDM group A, then assignedto a CDM group B, and lastly assigned to a CDM group C.

All cases of indicating a co-scheduled CDM group according to thespecific rule are represented as Table 75 below.

TABLE 75 Co-scheduled CDM DMRS CDM group used by group used by Caseconfiguration specific terminal another terminal Case 1 ConfigurationComb pattern A None Case 2 type 1 Comb pattern A Comb pattern B Case 3Comb pattern B Comb pattern A Case 4 Comb pattern A, B No need forindication Case 5 Configuration CDM group A None Case 6 type 2 CDM groupA CDM group B Case 7 CDM group A CDM group B, C Case 8 CDM group B CDMgroup A Case 9 CDM group B CDM group A, C Case 10 CDM group C CDM groupA, B Case 11 CDM group A, B None Case 12 CDM group A, B CDM group C Case13 CDM group A, B, C No need for indication

Referring to Table 75, when a Comb pattern A is used for a specificterminal, a co-scheduled CDM group used by another terminal may not bepresent (Case 1), or a Comb pattern B may be co-scheduled (Case 2).

Referring to Table 75, when a Comb pattern B is used for a specificterminal, in an MU-MIMO, total antenna ports used for a plurality ofterminals may be assigned to a Comb pattern A, and then assigned to aComb pattern B, thus a co-scheduled CDM group becomes always a Combpattern A (Case 3).

Referring to Table 75, when a Comb pattern A and a Comb pattern B areall used for a specific terminal, there is no need for additionallyindicating a co-scheduled CDM group (Case 4).

Referring to Table 75, when a CDM group A is used for a specificterminal, a co-scheduled CDM group used by another terminal may not bepresent (Case 5), a CDM group B may be co-scheduled (Case 6), or a CDMgroup B and a CDM group C may be co-scheduled (Case 7).

Referring to Table 75, when a CDM group B is used for a specificterminal, in an MU-MIMO, total antenna ports used for a plurality ofterminals are assigned to a CDM group A, and then assigned to a CDMgroup B, thus a co-scheduled CDM group used by another terminal may be aCDM group A (Case 8), or may be a CDM group A and a CDM group C (Case9).

Referring to Table 75, when a CDM group C is used for a specificterminal, in an MU-MIMO, total antenna ports used for a plurality ofterminals are assigned to a CDM group A and a CDM group B, and thenassigned to a CDM group C, thus a co-scheduled CDM group used by anotherterminal always becomes a CDM group A and a CDM group B (Case 10).

Referring to Table 75, when a CDM group A and a CDM group B are used fora specific terminal, a co-scheduled CDM group used by other terminal maynot be present (Case 11), or a CDM group C may be co-scheduled (Case12).

Referring to Table 75, when a CDM group A, a CDM group B, and a CDMgroup C are all used for a specific terminal, there is no need forindicating a CDM group used with another terminal (Case 13).

Meanwhile, a co-scheduled CDM group used by another terminal may berepresented in a number of co-scheduled CDM groups which is additionallyconsidered. Accordingly, Table 75 is represented in another method asTable 76 below.

TABLE 76 Additionally considered DMRS CDM group used by number ofco-scheduled Case configuration specific terminal CDM groups Case 1Configuration Comb pattern A 0 Case 2 type 1 Comb pattern A 1 (Combpattern B) Case 3 Comb pattern B 1 (Comb pattern A) Case 4 Comb patternA, B 0 Case 5 Configuration CDM group A 0 Case 6 type 2 CDM group A 1(CDM group B) Case 7 CDM group A 2 (CDM group B, C) Case 8 CDM group B 1(CDM group A) Case 9 CDM group B 2 (CDM group A, C) Case 10 CDM group C2 (CDM group A, B) Case 11 CDM group A, B 0 Case 12 CDM group A, B 1(CDM group C) Case 13 CDM group A, B, C 0

Referring to Table 76, as a case of a first DMRS configuration type,when a Comb pattern A is used for a specific terminal, a number ofadditionally considered co-scheduled CDM groups may be 0 (Case 1), ormay be 1 (Case 2, herein, a Comb pattern B is co-scheduled).

Referring to Table 76, as a case of a first DMRS configuration type,when a Comb pattern B is used for a specific terminal, in an MU-MIMO,total antenna ports used for a plurality of terminals are assigned to aComb pattern A, and then assigned to a Comb pattern B, thus a number ofadditionally considered co-scheduled CDM groups always becomes 1 (Case3, herein, a Comb pattern A is co-scheduled).

Referring to Table 76, as a case of a first DMRS configuration type,when a Comb pattern A and a Comb pattern B are used for a specificterminal, an additionally considered co-scheduled CDM group is notpresent, thus a number of thereof always becomes 0 (Case 4).

Referring to Table 76, as a case of a second DMRS configuration type,when a CDM group A is used for a specific terminal, a number ofadditionally considered co-scheduled CDM groups may be 0 (Case 5), maybe 1 (Case 6, herein, a CDM group B is co-scheduled), or may be 2 (Case7, herein, a CDM group B and a CDM group C are co-scheduled).

Referring to Table 76, as a case of a second DMRS configuration type,when a CDM group B is used for a specific terminal, in an MU-MIMO, totalantenna ports used for a plurality of terminals are assigned to a CDMgroup A, and then assigned to a CDM group B, thus a number ofadditionally considered co-scheduled CDM groups may be 1 (Case 8,herein, a CDM group A is co-scheduled), or may be 2 (Case 9, herein, aCDM group A and a CDM group C are co-scheduled).

Referring to Table 76, as a case of a second DMRS configuration type,when a CDM group C is used for a specific terminal, in an MU-MIMO, totalantenna ports used for a plurality of terminals are assigned to a CDMgroup A and a CDM group B, and then assigned to a CDM group C, thus anumber of additionally considered co-scheduled CDM groups always becomes2 (Case 10, herein, a CDM group A and a CDM group B are co-scheduled).

Referring to Table 76, as a case of a second DMRS configuration type,when a CDM group A and a CDM group B are used for a specific terminal, anumber of additionally considered co-scheduled CDM groups may be 0 (Case11), or may be 1 (Case 12, herein, a CDM group C is co-scheduled).

Referring to Table 76, as a case of a second DMRS configuration type,when a CDM group A, a CDM group B, and a CDM group C are used for aspecific terminal, an additionally considered co-scheduled CDM group isnot present, thus a number of additionally considered co-scheduled CDMgroups always becomes 0 (Case 13).

Hereinafter, an antenna port number configured according to a number ofcodewords and a number of layers will be described. Herein, it isassumed that up to two codewords are used. For each terminal, when oneto four layers are used, one codeword (codeword 0) may be used, and whenfive to eight layers are used, two codewords (codeword 0, codeword 1)may be used.

When one layer is used in a first DMRS configuration type based on anIFDMA, codeword 0 may be used as any one of DMRS antenna ports #0 to #7(#1, #2, #3, #4, #5, #6, or #7) (enabled). Herein, codeword 1 is notused (disabled).

When two layers are used in a first DMRS configuration type, codeword 0is used as antenna ports #0˜#1, #2˜#3, #4˜#5, or #6˜#7. When a Combpattern is configured with one symbol, considering that a Comb pattern Ais assigned to antenna ports {#0, #1}, and a Comb pattern B is assignedto antenna ports {#2, #3}, DMRS antenna ports for two layers may be {#0,#1} or {#2, #3}. In addition, when a Comb pattern is configured with twosymbols, considering that a Comb pattern A is assigned to antenna ports{#0, #1, #4, #5}, and a Comb pattern B is assigned to antenna ports {#2,#3, #6, #7}, DMRS antenna ports for two layer may be {#0, #1}, {#4, #5},{#2, #3}, or {#6, #7}. Herein, codeword 1 is not used.

When three layers are used in a first DMRS configuration type, codeword0 may be used as antenna ports #0˜#2, #0/#1/#4, or #2/#3/#6. When a Combpattern is configured with one symbol, considering that a Comb pattern Ais assigned to antenna ports {#0, #1}, and a Comb pattern B is assignedto antenna ports {#2, #3}, DMRS antenna ports for three layers may be{#0, #1, #2}. In addition when a Comb pattern is configured with twosymbols, considering that a Comb pattern A is assigned to antenna ports{#0, #1, #4, #5}, and a Comb pattern B is assigned to antenna ports {#2,#3, #6, #7}, DMRS antenna ports for three layers may be {#0, #1, #4}, or{#2, #3, #6}. Herein, codeword 1 is not used.

When four layers are used in a first DMRS configuration type, codeword 0may be used as antenna ports #0˜#3, #0/#1/#4/#5, or #2/#3/#6/#7. When aComb pattern is configured with one symbol, considering that a Combpattern A is assigned to antenna ports {#0, #1}, and a Comb pattern B isassigned to antenna ports {#2, #3}, DMRS antenna ports for four layersmay be {#0, #1, #2, #3}. In addition, when a Comb pattern is configuredwith two symbols, considering that a Comb pattern A is assigned toantenna ports {#0, #1, #4, #5}, and a Comb pattern B is assigned toantenna ports {#2, #3, #6, #7}, DMRS antenna ports for three layers maybe {#0, #1, #4, #5}, or {#2, #3, #6, #7}. Herein, codeword 1 is notused.

When five layers are used in a first DMRS configuration type, codeword 0may be used as antenna ports #0˜#1, and codeword 1 may be used asantenna ports #2/#3/#6. When a Comb pattern is configured with twosymbols, considering that a Comb pattern A is assigned to antenna ports{#0, #1, #4, #5}, and a Comb pattern B is assigned to antenna ports {#2,#3, #6, #7}, DMRS antenna ports for five layers may be {#0, #1} forcodeword 0, and {#2, #3, #6} for codeword 1. In other words, antennaports transmitted through codeword 0 may correspond to two antenna portsin order from the lowest antenna port index among antenna portscorresponding to a Comb pattern A, and antenna ports transmitted throughcodeword 1 may correspond to three antenna ports in order from thelowest antenna port index among antenna ports corresponding to a Combpattern B.

When six layers are used in a first DMRS configuration type, codeword 0may be used as antenna ports #0/#1/#4 and codeword 1 may be used asantenna ports #2/#3/#6. When a Comb pattern is configured with twosymbols, considering that a Comb pattern A is assigned to antenna ports{#0, #1, #4, #5}, and a Comb pattern B assigned to antenna ports {#2,#3, #6, #7}, DMRS antenna ports for six layers may be {#0, #1, #4} forcodeword 0 and {#2, #3, #6} for codeword 1. In other words, antennaports transmitted through codeword 0 may correspond to three antennaports in order from the lowest antenna port index among antenna portscorresponding to a Comb pattern A, and antenna ports transmitted throughcodeword 1 may correspond to three antenna ports in order from thelowest antenna port index among antenna ports corresponding to a Combpattern B.

When seven layers are used in a first DMRS configuration type, codeword0 may be used as antenna ports #0/#1/#4 and codeword 1 may be used asantenna ports #2/#3/#6/#7. When a Comb pattern is configured with twosymbols, considering that a Comb pattern A is assigned to antenna ports{#0, #1, #4, #5}, and a Comb pattern B is assigned to antenna ports {#2,#3, #6, #7}, DMRS antenna port for seven layers may be {#0, #1, #4} forcodeword 0 and {#2, #3, #6, #7} for codeword 1. In other words, antennaports transmitted through codeword 0 may correspond to three antennaports in order from the lowest antenna port index among antenna portscorresponding to a Comb pattern A, and antenna ports transmitted throughcodeword 1 may correspond to four antenna ports in order from the lowestantenna port index among antenna ports corresponding to a Comb patternB.

When eight layers are used in a first DMRS configuration type, codeword0 may be used as antenna ports #0/#1/#4/#5 and codeword 1 may be used asantenna ports #2/#3/#6/#7. When a Comb pattern is configured with twosymbols, considering that a Comb pattern A is assigned to antenna ports{#0, #1, #4, #5}, and a Comb pattern B is assigned to antenna ports {#2,#3, #6, #7}, DMRS antenna ports for eight layers may be {#0, #1, #4, #5}for codeword 0 and {#2, #3, #6, #7} for codeword 1. In other words,antenna ports transmitted through codeword 0 may correspond to fourantenna ports in order from the lowest antenna port index among antennaports corresponding to a Comb pattern A, and antenna ports transmittedthrough codeword 1 may correspond to four antenna ports in order fromthe lowest antenna port index among antenna ports corresponding to aComb pattern B.

Meanwhile, when one layer is used in a second DMRS configuration typebased on a CDM, codeword 0 may be used as any one of DMRS antenna ports#0 to #11 (#1, #2, #3, #4, #5, #6, #7, #8, #9, #10, or #11). Herein,codeword 1 is not used.

When two layers are used in a second DMRS configuration type, codeword 0may be used as antenna ports #0˜#1, #2˜#3, #4˜#5, #6˜#7, #8˜#9, or#10˜#11. When a CDM group is configured with one symbol, consideringthat a CDM group A is assigned to antenna ports {#0, #1}, a CDM group Bis assigned to antenna ports {#2, #3}, and a CDM group C is assigned toantenna ports {#4, #5}, DMRS antenna ports for two layers may be {#0,#1}, {#2, #3}, or {#4, #5}. In addition, when a CDM group is configuredwith two symbols, considering that a CDM group A is assigned to antennaports {#0, #1, #6, #7}, a CDM group B is assigned to antenna ports {#2,#3, #8, #9}, and a CDM group C is assigned to antenna ports {#4, #5,#10, #11}, DMRS antenna ports for two layers may be {#0, #1}, {#6, #7},{#2, #3}, {#8, #9}, {#4, #5}, or {#10, #11}. Herein, codeword 1 is notused.

When three layers are used in a second DMRS configuration type, codeword0 may be used as antenna ports #0˜#2, #3˜#5, #0/#1/#6, #2/#3/#8,#4/#5/#10, or #7/#9/#11. When a CDM group is configured with one symbol,considering that a CDM group A is assigned to antenna ports {#0, #1}, aCDM group B is assigned to antenna ports {#2, #3}, and a CDM group C isassigned to antenna ports {#4, #5}, DMRS antenna port for three layersmay be {#0, #1, #2}, or {#3, #4, #5}. In addition, when a CDM group isconfigured with two symbols, considering that a CDM group A is assignedto antenna ports {#0, #1, #6, #7}, a CDM group B is assigned to antennaports {#2, #3, #8, #9}, and a CDM group C is assigned to antenna ports{#4, #5, #10, #11}, DMRS antenna ports for three layers may be {#0, #1,#6}, {#2, #3, #8}, {#4, #5, #10}, or {#7, #9, #11}. Herein, antennaports {#7, #9, #11} may not be used. Herein, codeword 1 is not used.

When four layers are used in a second DMRS configuration type, codeword0 may be used as antenna ports #0˜#3, #0/#1/#6/#7, #2/#3/#8/#9, or#4/#5/#10/#11. When a CDM group is configured with one symbol,considering that a CDM group A is assigned to antenna ports {#0, #1}, aCDM group B is assigned antenna ports {#2, #3}, and a CDM group C isassigned to antenna ports {#4, #5}, DMRS antenna ports for four layersmay be {#0, #1, #2, #3}. In addition, when a CDM group is configuredwith two symbols, considering that a CDM group A is assigned to antennaports {#0, #1, #6, #7}, a CDM group B is assigned to antenna ports {#2,#3, #8, #9}, and a CDM group C is assigned to antenna ports {#4, #5,#10, #11}, DMRS antenna ports for four layers may be {#0, #1, #6, #7},{#2, #3, #8, #9}, or {#4, #5, #10, #11}. Herein, codeword 1 is not used.

When five layers are used in a second DMRS configuration type, codeword0 may be used as antenna ports #0˜#1, and codeword 1 may be used asantenna ports #2˜#4. This corresponds to a case where a CDM group isconfigured with one symbol, considering that CDM group A is assigned toantenna ports {#0, #1}, a CDM group B is assigned to antenna ports {#2,#3}, and a CDM group C is assigned to antenna ports {#4, #5}, DMRSantenna ports for five layers may be {#0, #1, #2, #3, #4}.

Alternatively, when five layers are used in a second DMRS configurationtype, codeword 0 may be used as antenna ports #0˜#1 and codeword 1 maybe used as antenna ports #2/#3/#8. This correspond to a case where a CDMgroup is configured with two symbols, considering that a CDM group A isassigned to antenna ports {#0, #1, #6, #7}, a CDM group B is assigned toantenna ports {#2, #3, #8, #9}, and a CDM group C is assigned to antennaports {#4, #5, #10, #11}, DMRS antenna ports for five layers may be {#0,#1, #2, #3, #8}. In other words, antenna ports transmitted throughcodeword 0 may correspond to two antenna ports in order from the lowestantenna port index among antenna ports corresponding to a CDM group A,and antenna ports transmitted through codeword 1 may correspond to threeantenna ports in order from the lowest antenna port index among antennaports corresponding to a CDM group B.

When six layers are used in a second DMRS configuration type, codeword 0may be used as antenna ports #0˜#2 and codeword 1 may be used as antennaport #3˜#5. This corresponds to a case where a CDM group is configuredwith one symbol, considering that a CDM group A is assigned to antennaports {#0, #1}, a CDM group B is assigned to antenna ports {#2, #3}, anda CDM group C is assigned to antenna ports {#4, #5}, DMRS antenna portsfor six layers may be {#0, #1, #2, #3, #4, #5}.

Alternatively, when six layers are used in a second DMRS configurationtype, codeword 0 may be used as antenna ports #0/#1/#6 and codeword 1 isused as antenna ports #2/#3/#8. This corresponds to a case where a CDMgroup is configured with two symbols, considering that a CDM group A isassigned to antenna ports {#0, #1, #6, #7}, a CDM group B is assigned toantenna ports {#2, #3, #8, #9}, and a CDM group C is assigned to antennaports {#4, #5, #10, #11}, DMRS antenna ports for six layers may be {#0,#1, #6, #2, #3, #8}. In other words, antenna ports transmitted throughcodeword 0 may correspond to three antenna ports in order from thelowest antenna port index among antenna ports corresponding to a CDMgroup A, and antenna ports transmitted through codeword 1 may correspondthree antenna ports in order from the lowest antenna port index amongantenna ports corresponding to a CDM group B.

When seven layers are used in a second DMRS configuration type, codeword0 may be used as antenna ports #0/#1/#6 and codeword 1 may be used asantenna ports #2/#3/#8/#9. This corresponds to a case where a CDM groupis configured with two symbols, considering that a CDM group A isassigned to antenna ports {#0, #1, #6, #7}, a CDM group B is assigned toantenna ports {#2, #3, #8, #9}, and a CDM group C is assigned to antennaports {#4, #5, #10, #11}, DMRS antenna ports for seven layers may be{#0, #1, #6, #2, #3, #8, #9}. In other words, antenna ports transmittedthrough codeword 0 may correspond to three antenna ports in order fromthe lowest antenna port index among antenna ports corresponding to a CDMgroup A, and antenna ports transmitted through codeword 1 may correspondto four antenna ports in order from the lowest antenna port index amongantenna ports corresponding to a CDM group B.

When eight layers are used in a second DMRS configuration type, codeword0 may be used as antenna ports #0/#1/#6/#7 and codeword 1 may be used asantenna ports #2/#3/#8/#9. This corresponds to a case where a CDM groupis configured with two symbols, considering that a CDM group A isassigned to antenna ports {#0, #1, #6, #7}, a CDM group B is assigned toantenna ports {#2, #3, #8, #9}, and a CDM group C is assigned to antennaports {#4, #5, #10, #11}, DMRS antenna ports for eight layers may be{#0, #1, #6, #7, #2, #3, #8, #9}. In other words, antenna portstransmitted through codeword 0 may correspond to four antenna ports inorder from the lowest antenna port index among antenna portscorresponding to a CDM group A, and antenna ports transmitted throughcodeword 1 may correspond to four antenna ports in order from the lowestantenna port index among antenna ports corresponding to a CDM group B.

Among the above cases, in a first DMRS configuration type using twosymbols, when a specific terminal transmits N DMRSs by using twocodewords (N=5, 6, 7, 8), antenna ports transmitted through codeword 0and antenna ports transmitted through codeword 1 of the two codewordsare antenna ports belonging to CDM groups different from each other. Indetail, antenna ports transmitted through codeword 0 may correspond to└N/2┘ antenna ports in order from the lowest antenna port index amongantenna ports corresponding to a Comb pattern A, and antenna portstransmitted through codeword 1 may correspond to ┌N/2┐ antenna ports inorder from the lowest antenna port index among antenna portscorresponding to a Comb pattern B.

In addition, among the above cases, in a second DMRS configuration typeusing two symbols, when a specific terminal transmits N DMRSs by usingtwo codewords (N=5, 6, 7, 8), antenna ports transmitted through codeword0 and antenna ports transmitted through codeword 1 of the two codewordsare antenna ports belonging to CDM groups different from each other. Indetail, antenna port transmitted through codeword 0 may correspond to└N/2┘ antenna ports in order from the lowest antenna port index amongantenna ports corresponding to a CDM group A, and antenna porttransmitted through codeword 1 may corresponds to ┌N/2┐ antenna ports inorder from the lowest antenna port index among antenna portscorresponding to a CDM group B.

Hereinafter, a method of configuring, by the base station, DMRSinformation in the NR system, and indicating the same will be described.

As a first embodiment, in case of a first DMRS configuration type basedon an IFDMA, the base station may indicate by using one table a numberof DMRS symbols (one or two), a number of layers, an antenna portnumber, a co-scheduled CDM group (or a number of co-scheduled CDMgroups) which are used by the terminal. Herein, a number of layers andan antenna port number in accordance therewith may consider the belowcases.

-   -   In a SU-MIMO, for a DMRS configuration using one symbol, up to        four layers an antenna port number in accordance therewith, and        for a DMRS configuration using two symbols, up to eight layers        an antenna port number in accordance therewith may be        classified.    -   In an MU-MIMO, for a DMRS configuration using one symbol, up to        two layers an antenna port number in accordance therewith, and        for a DMRS configuration using two symbols, up to four layers        and an antenna port number in accordance therewith may be        classified for each terminal.    -   In an MU-MIMO, for a DMRS configuration using one symbol, up to        four layers and an antenna port number in accordance therewith,        and for a DMRS configuration using two symbols, up to eight        layers and an antenna port number in accordance therewith may be        classified for across all terminals.    -   For rate-matching, a co-scheduled CDM group may be indicated.        However, herein, rather than indicating all co-scheduled CDM        groups for another terminals, when the base station indicates a        scheduled CDM group for a corresponding terminal, and the base        station may indicate co-scheduled CDM groups (or a number of        co-scheduled CDM groups) according to the ruled mentioned in        Tables 7 and 8.

Herein, the table may be indicated by being included in a signalingfield of downlink control information (DCI) for each terminal.

When indicating one codeword (when codeword 0 is used and codeword 1 isnot used), the table may be as Table 77 below.

TABLE 77 (Number of) Bit Number of Number of Antenna port Co-scheduledvalue Symbol(s) layer(s) number CDM group(s) 0 1 1 #0 0 1 1 1 #0 1 (Combpattern B) 2 1 1 #1 0 3 1 1 #1 1 (Comb pattern B) 4 1 1 #2 1 (Combpattern A) 5 1 1 #3 1 (Comb pattern A) 6 1 2 #0, #1 0 7 1 2 #0, #1 1(Comb pattern B) 8 1 2 #2, #3 1 (Comb pattern A) 9 1 3 #0~#2 0 10 1 4#0~#3 0 11 2 1 #0 0 12 2 1 #0 1 (Comb pattern B) 13 2 1 #1 0 14 2 1 #1 1(Comb pattern B) 15 2 1 #2 1 (Comb pattern A) 16 2 1 #3 1 (Comb patternA) 17 2 1 #4 0 18 2 1 #4 1 (Comb pattern B) 19 2 1 #5 0 20 2 1 #5 1(Comb pattern B) 21 2 1 #6 1 (Comb pattern A) 22 2 1 #7 1 (Comb patternA) 23 2 2 #0, #1 0 24 2 2 #0, #1 1 (Comb pattern B) 25 2 2 #2, #3 1(Comb pattern A) 26 2 2 #4, #5 0 27 2 2 #4, #5 1 (Comb pattern B) 28 2 2#6, #7 1 (Comb pattern A) 29 2 3 #0, #1, #4 0 30 2 3 #0, #1, #4 1 (Combpattern B) 31 2 3 #2, #3, #6 1 (Comb pattern A) 32 2 4 #0, #1, #4, #5 033 2 4 #0, #1, #4, #5 1 (Comb pattern B) 34 2 4 #2, #3, #6, #7 1 (Combpattern A) 35 Reserved . . . . . . 63 Reserved

In Table 77, bit values may be out of order, and messages included inTable 77 may be identical. Detailed content thereof may follow contentof FIGS. 22 to 26 and Tables 70 to 76.

In Table 77, a DMRS antenna port corresponding to a Comb pattern A and aComb pattern B are as follows.

In case of a first DMRS configuration type using one symbol, DMRSantenna ports corresponding to a Comb pattern A is #0 and #1, and DMRSantenna ports corresponding to a Comb pattern B are #2 and #3.

In case of a first DMRS configuration type using two symbols, DMRSantenna ports corresponding to a Comb pattern A are #0, #1, #4, and #5,and DMRS antenna ports corresponding to a Comb pattern B are #2, #3, #6,and #7.

Herein, a Comb pattern group is configured with antenna ports using thesame RE pattern. The antenna ports may share the same RE resources,classified into CS values or FD-OCCs or both, and may be defined as aCDM group as like as a second DMRS configuration type.

Meanwhile, when indicating two codewords (when codeword 0 and codeword 1are used), the table is as Table 78 below.

TABLE 78 (Number of) Bit Number of Number of Antenna port Co-scheduledvalue Symbol(s) layer(s) number CDM group(s) 0 2 5 #0, #1, 0 #2, #3, #61 2 6 #0, #1, #4, 0 #2, #3, #6 2 2 7 #0, #1, #4, 0 #2, #3, #6, #7 3 2 8#0, #1, #4, #5, 0 #2, #3, #6, #7 4 Reserved . . . . . . 63  Reserved

In Table 78, bit values may be out of order, but messages included inTable 78 may be identical. Detailed content thereof may follow contentof FIGS. 22 to 26 and Tables 70 to 76.

Meanwhile, in a case of a first DMRS configuration type based on anIFDMA, the base station may indicate a number of DMRS symbols (one ortwo), a number of layers, an antenna port number and a co-scheduled CDMgroup (or a number of co-scheduled CDM groups) which are used for acorresponding terminal by using two tables by codewords (a firstaccording to Table 9, and a second table according to Table 10). Herein,the first table actually includes 35 types of bit values excluding a“Reserved” bit value (bit value 0˜bit value 34). The second tableactually includes four types of bit values excluding a “Reserved” bitvalue (bit value 0˜bit value 3). Values of the respective tables may beindicated by using a signaling field of 6 bits and which is included inDCI. This is because, signaling of 6 bits is required in order toconfigure up to 35 types configurations of Table 77.

In addition, in a case of a first DMRS configuration type based on anIFDMA, the base station may indicate a number of DMRS symbols (one ortwo), a number layers, an antenna port number, and a co-scheduled CDMgroup (or a number of co-scheduled CDM groups) which are used for acorresponding terminal by using three tables by codewords. Herein, afirst table may be configured with cases of using one symbol in Table77. In other words, in the first table, a configuration of using onesymbol and using one codeword among configurations of Table 77 may beincluded. Herein, the first table actually includes 11 types of bitvalues excluding a “Reserved” bit value (bit value 0˜bit value 10). Asecond table may be configured with cases using two symbols in Table 77.In other words, in the second table, a configuration using two symbolsand using one codeword may be included. Herein, the second tableactually includes 24 types of bit values excluding a “Reserved” bitvalue (bit value 11˜bit value 34). A third table may be configured asTable 78. Herein, the third table actually includes 4 types of bitvalues excluding a “Reserved” bit value (bit value 0˜bit value 3).Values of the respective tables may be indicated by using a signalingfield with 5 bits and which is included in DCI. This is becausesignaling of 5 bits is required in order to configure up to 24 typesconfigurations of Table 77. Herein, by using an additional signalingfield having 1 bit and which is included in DCI, whether a correspondingtable is configured with one symbol or with two symbols may beindicated.

Meanwhile, in case of a second DMRS configuration type based on a CDM,the base station may indicate a number of DMRS symbols (one or two), anumber layers, an antenna port number, and a co-scheduled CDM group (ora number of co-scheduled CDM groups) which are used for a correspondingterminal by using one table. Herein, a number layers and an antenna portnumber in association therewith may consider the cases below.

-   -   In a SU-MIMO, for a DMRS configuration using one symbol, up to        six layers and an antenna port number in association therewith,        and for a DMRS configuration using two symbols, up to eight        layers and an antenna port number in association therewith may        be respectively classified.    -   In an MU-MIMO, for a DMRS configuration using one symbol, up to        four layers and an antenna port number in association therewith,        and for a DMRS configuration using two symbols, up to four        layers and an antenna port number in association therewith may        be respectively classified for each terminal.    -   In an MU-MIMO, for a DMRS configuration using one symbol, up to        six layers and an antenna port number in association therewith,        and for a DMRS configuration using two symbols, up to twelve        layers and an antenna port number in association therewith may        be classified for across all terminals.    -   For rate-matching, a co-scheduled CDM group may be indicated.        However, herein, rather than indicating all co-scheduled CDM        groups for another terminal when the base station indicates a        scheduled CDM group for a corresponding terminal, the base        terminal may indicate a scheduled CDM group according to the        rule mentioned with Tables 75 and 76 (or a number of        co-scheduled CDM groups).

Herein, the table may be indicated by being including in a signalingfield of DCI for each terminal.

When indicating one codeword (when codeword 0 is used and codeword 1 isnot used), the table becomes as Table 79 below.

TABLE 79 (Number of) Bit Number of Number of Antenna port Co-scheduledvalue Symbol(s) layer(s) number CDM group(s) 0 1 1 #0 0 1 1 1 #0 1 (CDMgroup B) 2 1 1 #0 2 (CDM group B, C) 3 1 1 #1 0 4 1 1 #1 1 (CDM group B)5 1 1 #1 2 (CDM group B, C) 6 1 1 #2 1 (CDM group A) 7 1 1 #2 2 (CDMgroup A, C) 8 1 1 #3 1 (CDM group A) 9 1 1 #3 2 (CDM group A, C) 10 1 1#4 2 (CDM group A, B) 11 1 1 #5 2 (CDM group A, B) 12 1 2 #0, #1 0 13 12 #0, #1 1 (CDM group B) 14 1 2 #0, #1 2 (CDM group B, C) 15 1 2 #2, #31 (CDM group A) 16 1 2 #2, #3 2 (CDM group A, C) 17 1 2 #4, #5 2 (CDMgroup A, B) 18 1 3 #0, #1, #2 0 19 1 3 #0, #1, #2 1 (CDM group C) 20 1 3#3, #4, #5 1 (CDM group A) 21 1 4 #0, #1, #2, #3 0 22 1 4 #0, #1, #2, #31 (CDM group C) 23 2 1 #0 0 24 2 1 #0 1 (CDM group B) 25 2 1 #0 2 (CDMgroup B, C) 26 2 1 #1 0 27 2 1 #1 1 (CDM group B) 28 2 1 #1 2 (CDM groupB, C) 29 2 1 #2 1 (CDM group A) 30 2 1 #2 2 (CDM group A, C) 31 2 1 #3 1(CDM group A) 32 2 1 #3 2 (CDM group A, C) 33 2 1 #4 2 (CDM group A, B)34 2 1 #5 2 (CDM group A, B) 35 2 1 #6 0 36 2 1 #6 1 (CDM group B) 37 21 #6 2 (CDM group B, C) 38 2 1 #7 0 39 2 1 #7 1 (CDM group B) 40 2 1 #72 (CDM group B, C) 41 2 1 #8 1 (CDM group A) 42 2 1 #8 2 (CDM group A,C) 43 2 1 #9 1 (CDM group A) 44 2 1 #9 2 (CDM group A, C) 45 2 1 #10  2(CDM group A, B) 46 2 1 #11  2 (CDM group A, B) 47 2 2 #0, #1 0 48 2 2#0, #1 1 (CDM group B) 49 2 2 #0, #1 2 (CDM group B, C) 50 2 2 #2, #3 1(CDM group A) 51 2 2 #2, #3 2 (CDM group A, C) 52 2 2 #4, #5 2 (CDMgroup B, C) 53 2 2 #6, #7 0 54 2 2 #6, #7 1 (CDM group B) 55 2 2 #6, #72 (CDM group B, C) 56 2 2 #8, #9 1 (CDM group A) 57 2 2 #8, #9 2 (CDMgroup A, C) 58 2 2 #10, #11 2 (CDM group B, C) 59 2 3 #0, #1, #6 0 60 23 #0, #1, #6 1 (CDM group B) 61 2 3 #0, #1, #6 2 (CDM group B, C) 62 2 3#2, #3, #8 1 (CDM group A) 63 2 3 #2, #3, #8 2 (CDM group A, C) 64 2 3 #4, #5, #10 2 (CDM group A, B) 65 2 3  #7, #9, #11 0 66 2 4 #0, #1, #6,#7 0 67 2 4 #0, #1, #6, #7 1 (CDM group B) 68 2 4 #0, #1, #6, #7 2 (CDMgroup B, C) 69 2 4 #2, #3, #8, #9 1 (CDM group A) 70 2 4 #2, #3, #8, #92 (CDM group A, C) 71 2 4  #4, #5, #10, 2 (CDM group A, B) #11 72Reserved . . . . . . 127 Reserved

In Table 79, bit values may be out of order, but messages include inTable 79 may be identical. Detailed content thereof may follow contentof FIGS. 22 to 26 and Tables 70 to 76.

In Table 79, a DMRS antenna port corresponding to a CDM group A, a CDMgroup B, and a CDM group C may be as follows.

In case of a second DMRS configuration type using one symbol, DMRSantenna ports corresponding to a CDM group A are #0 and #1, DMRS antennaports corresponding to a CDM group B are #2 and #3, and DMRS antennaports corresponding to a CDM group C are #4 and #5.

In case of a second DMRS configuration type using two symbols, DMRSantenna ports corresponding to a CDM group A are #0, #1, #6, and #7,DMRS antenna ports corresponding to a CDM group B are #2, #3, #8, and#9, and DMRS antenna ports corresponding to a CDM group C are #4, #5,#10, and #11.

Herein, a CDM group is configured with antenna ports using the same REpattern. The antenna ports may share the same RE resources, and may beclassified into FD-OCCs or FD-OCCs or both.

Meanwhile, when indicating two codewords (when codeword 0 and codeword 1are used), the table becomes as Table 80 below.

TABLE 80 (Number of) Bit Number of Number of Antenna port Co-scheduledvalue Symbol(s) layer(s) number CDM group(s) 0 1 5 #0, #1, 0 #2, #3, #41 1 6 #0, #1, #2, 0 #3, #4, #5 2 2 5 #0, #1, 0 #2, #3, #8 3 2 6 #0, #1,#6, 0 #2, #3, #8 4 2 7 #0, #1, #6, 0 #2, #3, #8, #9 5 2 8 #0, #1, #6, #70 #2, #3, #8, #9 6 Reserved . . . . . . 127  Reserved

In Table 80, bit values may be out of order, but messages included inTable 12 may be identical. Detailed content thereof may follow contentsof FIGS. 22 to 26 and Tables 70 to 76.

Meanwhile, in case of a second DMRS configuration type based on a CDM,the base station may indicate a number of DMRS symbols (one or two), anumber layers, an antenna port number, and a co-scheduled CDM group (ora number of co-scheduled CDM groups) which are used for a correspondingterminal by using two tables by codewords (a first table according toTable 79 and a second table according to Table 80). Herein, the firsttable actually includes 72 types of bit values excluding a “Reserved”bit value (bit value 0˜bit value 71). The second table actually includes6 types of bit values excluding a “Reserved” bit value (bit value 0˜bitvalue 5). Values of the respective tables may be indicated by usingsignaling filed with 7 bits and which is included in DCI. This isbecause, signaling of 7 bits is required in order to configure up 72types of configurations of Table 79.

In addition, in case of a second DMRS configuration type based on a CDM,the base station may indicate a number of DMRS symbols (one or two), anumber layers, an antenna port number, and a co-scheduled CDM group (ora number of co-scheduled CDM groups) which are used for a correspondingterminal by using four tables by symbols and codewords. Herein, a firsttable may be configured with cases using one symbol in Table 79. Inother words, the first table may include configurations using one symboland using one codeword among configurations of Table 79. Herein, thefirst table actually includes 23 types of bit value excluding a“Reserved” bit value (bit value 0˜bit value 22). A second table may beconfigured with cases using two symbols in Table 79. In other words, thesecond table may include configurations using two symbols and using onecodeword among configurations of Table 79. Herein, the second tableactually includes 49 types of bit values excluding a “Reserved” bitvalue (bit value 23˜bit value 71). A third table may be configured withcases using one symbol in Table 80. In other words, the third table mayinclude configurations using one symbol and using two codewords of Table80. Herein, the third table actually includes 2 types of bit valuesexcluding a “Reserved” bit value (bit value 0 bit value 1). A fourthtable may be configured with cases using two symbols in Table 80. Inother words, the fourth table includes configurations using two symbolsand using two codewords of Table 80. Herein, the fourth table actuallyincludes four types of bit value excluding a “Reserved” bit value (bitvalue 2˜bit value 5). Values of the respective tables may be indicatedby using a signaling field with 6 bits and which is included in DCI.This is because, signaling of 6 bits is required to configure up 49types of configurations using two symbols in Table 11. Herein, by usingan additional signaling field of 1 bit, whether a corresponding table isconfigured with one symbol or two symbols may be indicated.

Meanwhile, in a case of a second DMRS configuration type based on a CDM,the remaining factors are identical. However, the base station mayfollow the rule mentioned with Table 81 below when indicating aco-scheduled CDM group for rate-matching.

TABLE 81 Number of additionally DMRS CDM group used by consideredco-scheduled Case configuration specific terminal CDM groups Case 1Configuration Comb pattern A 0 Case 2 type 1 Comb pattern A 1 (Combpattern B) Case 3 Comb pattern B 1 (Comb pattern A) Case 4 Comb patternA, B 0 Case 5 Configuration CDM group A 0 Case 6 type 2 CDM group A 2(CDM group B, C) Case 7 CDM group B 1 (CDM group A) Case 8 CDM group B 2(CDM group A, C) Case 9 CDM group C 2 (CDM group A, B) Case 10 CDM groupA, B 0 Case 11 CDM group A, B 1 (CDM group C) Case 12 CDM group A, B, C0

In Table 76, for a second DMRS configuration type, when a CDM group usedby a specific terminal is a CDM group A, a number of additionallyconsidered co-scheduled CDM groups is classified into three cases: maybe 0, may be 1 (herein, a CDM group B is co-scheduled), or may be 2(herein, a CDM group B and a CDM group C are co-scheduled).

However, in Table 81, for a second DMRS configuration type, when a CDMgroup used by a specific terminal is a CDM group A, a number ofadditionally considered co-scheduled CDM groups is classified into twocases: may be 0, or may be 1 or 2 (herein, a CDM group B isco-scheduled, or a CDM group B and a CDM group C are co-scheduled).

In other words, in Table 81, in order to reduce a number of cases, for asecond DMRS configuration type, when a CDM group used by a specificterminal is a CDM group A, a number of additionally consideredco-scheduled CDM groups may be signaled by combining a case where anumber of co-scheduled CDM groups is one and a case of being two.Herein, the terminal may not obtain information of whether aco-scheduled CDM group is one or two, thus rate-matching is performed byassuming that the co-scheduled CDM group is two. Accordingly, Table 79may be changed to Table 82 below according to the rule mentioned inTable 81. However, herein, Table 80 may be used as it is.

TABLE 82 (Number of) Bit Number of Number of Antenna port Co-scheduledvalue Symbol(s) layer(s) number CDM group(s) 0 1 1 #0 0 1 1 1 #0 2 (CDMgroup B, C) 2 1 1 #1 0 3 1 1 #1 2 (CDM group B, C) 4 1 1 #2 1 (CDM groupA) 5 1 1 #2 2 (CDM group A, C) 6 1 1 #3 1 (CDM group A) 7 1 1 #3 2 (CDMgroup A, C) 8 1 1 #4 2 (CDM group A, B) 9 1 1 #5 2 (CDM group A, B) 10 12 #0, #1 0 11 1 2 #0, #1 2 (CDM group B, C) 12 1 2 #2, #3 1 (CDM groupA) 13 1 2 #2, #3 2 (CDM group A, C) 14 1 2 #4, #5 2 (CDM group A, B) 151 3 #0, #1, #2 0 16 1 3 #0, #1, #2 1 (CDM group C) 17 1 3 #3, #4, #5 1(CDM group A) 18 1 4 #0, #1, #2, #3 0 19 1 4 #0, #1, #2, #3 1 (CDM groupC) 20 2 1 #0 0 21 2 1 #0 2 (CDM group B, C) 22 2 1 #1 0 23 2 1 #1 2 (CDMgroup B, C) 24 2 1 #2 1 (CDM group A) 25 2 1 #2 2 (CDM group A, C) 26 21 #3 1 (CDM group A) 27 2 1 #3 2 (CDM group A, C) 28 2 1 #4 2 (CDM groupA, B) 29 2 1 #5 2 (CDM group A, B) 30 2 1 #6 0 31 2 1 #6 2 (CDM group B,C) 32 2 1 #7 0 33 2 1 #7 2 (CDM group B, C) 34 2 1 #8 1 (CDM group A) 352 1 #8 2 (CDM group A, C) 36 2 1 #9 1 (CDM group A) 37 2 1 #9 2 (CDMgroup A, C) 38 2 1 #10  2 (CDM group A, B) 39 2 1 #11  2 (CDM group A,B) 40 2 2 #0, #1 0 41 2 2 #0, #1 2 (CDM group B, C) 42 2 2 #2, #3 1 (CDMgroup A) 43 2 2 #2, #3 2 (CDM group A, C) 44 2 2 #4, #5 2 (CDM group B,C) 45 2 2 #6, #7 0 46 2 2 #6, #7 2 (CDM group B, C) 47 2 2 #8, #9 1 (CDMgroup A) 48 2 2 #8, #9 2 (CDM group A, C) 49 2 2 #10, #11 2 (CDM groupB, C) 50 2 3 #0, #1, #6 0 51 2 3 #0, #1, #6 2 (CDM group B, C) 52 2 3#2, #3, #8 1 (CDM group A) 53 2 3 #2, #3, #8 2 (CDM group A, C) 54 2 3 #4, #5, #10 2 (CDM group A, B) 55 2 3  #7, #9, #11 0 56 2 4 #0, #1, #6,#7 0 57 2 4 #0, #1, #6, #7 2 (CDM group B, C) 58 2 4 #2, #3, #8, #9 1(CDM group A) 59 2 4 #2, #3, #8, #9 2 (CDM group A, C) 60 2 4  #4, #5,#10, 2 (CDM group A, B) #11 61 Reserved 62 Reserved 63 Reserved

Meanwhile, in case of a second DMRS configuration type, the base stationmay indicate a number of DMRS symbols (one or two), a number layers, anantenna port number, and a co-scheduled CDM group (or a number ofco-scheduled CDM groups) which are used by a corresponding terminal byusing two tables by codewords (a first table according to Table 82 and asecond table according to Table 13). Herein, the first table actuallyincludes 61 types of bit value excluding a “Reserved” bit value (bitvalue 0˜bit value 60). The second table actually includes 6 types of bitvalues excluding a “Reserved” bit value (bit value 0˜bit value 5).Values of the respective tables may be indicated by using a signalingfield with 6 bits which is included in DCI. This is because signaling of6 bits is required in order to configure up to 61 types ofconfigurations of Table 82.

As a second embodiment, the second embodiment is identical to the firstembodiment for a first DMRS configuration type. For a second DMRSconfiguration type, the base station follows the rule mentioned inTables 81 and 82. However, when indicating a co-scheduled CDM group forrate-matching, the base station may follow the rule mentioned in Table83 below rather than following the rule mentioned in Tables 75 and 76.

TABLE 83 Additionally considered DMRS CDM group used by co-scheduledCase configuration specific terminal CDM group type Case 1 ConfigurationComb pattern A 0 Case 2 type 1 Comb pattern A 1 Case 3 Comb pattern B 0Case 4 Comb pattern A, B 0 Case 5 Configuration CDM group A 0 Case 6type 2 CDM group A 1 Case 7 CDM group B 0 Case 8 CDM group B 1 Case 9CDM group C 0 Case 10 CDM group A, B 0 Case 11 CDM group A, B 1 Case 12CDM group A, B, C 0

Referring to Table 83, as a value for an additionally consideredco-scheduled CDM group type, 0 or 1 is indicated. When the value is 0,for a first DMRS configuration type, 1) when a CDM group used by aspecific terminal is a Comb pattern A, it is considered that a Combpattern A is used for all terminals paired for an MU-MIMO (Case 1), 2)when a CDM group used by a specific terminal is a Comb pattern B, it isconsidered that a Comb pattern A and a Comb pattern B are used for allterminals paired for an MU-M (Case 3, it is assumed that a Comb patternA is assigned, and then a Comb pattern B is assigned), 3) when a CDMgroup used by a specific terminal is a Comb pattern A and a Comb patternB, it is considered that a Comb pattern A and a Comb pattern B are usedfor all terminals paired for an MU-MIMO (Case 4).

In addition, when the value is 0, for a second DMRS configurationtype, 1) when a CDM group used by a specific terminal is a CDM group A,it is considered that a CDM group A is used for all terminals paired foran MU-MIMO (Case 5), 2) when a CDM group used by a specific terminal isa CDM group B, it is considered that a CDM group A and a CDM group B areused for all terminals paired for an MU-MI (Case 7, it is assumed that aCDM group A is assigned, and then a CDM group B is assigned), 3) when aCDM group used by a specific terminal is a CDM group C, it is consideredthat a CDM group A, a CDM group B, and a CDM group C are used for allterminals paired for an MU-MI (Case 9, it is assumed that a CDM group Ais assigned, then a CDM group B is assigned, and then a CDM group C isassigned), 4) when a CDM group used by a specific terminal is a CDMgroup A and a CDM group B, it is considered that a CDM group A and a CDMgroup B are used for all terminals paired in an MU-MIMO (Case 10), 5)when a CDM group used by a specific terminal is a CDM group A, a CDMgroup B, and a CDM group C, it is considered that a CDM group A, a CDMgroup B, and a CDM group C are used for all terminal paired for anMU-MIMO (Case 11).

In other words, when a value for an additionally considered co-scheduledCDM group type is indicated as 0, until a CDM group used by a specificterminal may be used for all terminals paired for an MU-MIMO. Forexample, when a CDM group used by a specific terminal is a CDM group A,until a CDM group A is assigned. When a CDM group used by a specificterminal is a CDM group B, a CDM group A is assigned and then a CDMgroup B is assigned, thus until a CDM group A and a CDM group B. When aCDM group used by a specific terminal is a CDM group C, a CDM group A isassigned, then a CDM group B is assigned, and then a CDM group C isassigned, thus a CDM group A, a CDM group B, and a CDM group C are allcorresponded.

When the value is 1, it is considered that a CDM group is used for allterminals paired for an MU-MIMO. In other words, in case of a first DMRSconfiguration type, it is considered that a Comb pattern A and a Combpattern B are both used (Case 2), and in case of a second DMRSconfiguration type, it is considered that a CDM group A, a CDM group B,and a CDM group C are all used (Case 6, Case 8, and Case 11).

Accordingly, when Table 15 is considered, for the second embodiment,Tables 84 and 85 below may be used for a first DMRS configuration type,and Tables 86 and 87 below may be used for a second DMRS configurationtype.

Table 85 below shows cases of indicating one codeword (codeword 0 isused and codeword 1 is not used) for a first DMRS configuration type.

TABLE 84 Type of Bit Number of Number of Antenna port Co-scheduled valueSymbol(s) layer(s) number CDM group(s) 0 1 1 #0 0 1 1 1 #0 1 2 1 1 #1 03 1 1 #1 1 4 1 1 #2 0 5 1 1 #3 0 6 1 2 #0, #1 0 7 1 2 #0, #1 1 8 1 2 #2,#3 0 9 1 3 #0~#2 0 10 1 4 #0~#3 0 11 2 1 #0 0 12 2 1 #0 1 13 2 1 #1 0 142 1 #1 1 15 2 1 #2 0 16 2 1 #3 0 17 2 1 #4 0 18 2 1 #4 1 19 2 1 #5 0 202 1 #5 1 21 2 1 #6 0 22 2 1 #7 0 23 2 2 #0, #1 0 24 2 2 #0, #1 1 25 2 2#2, #3 0 26 2 2 #4, #5 0 27 2 2 #4, #5 1 28 2 2 #6, #7 0 29 2 3 #0, #1,#4 0 30 2 3 #0, #1, #4 1 31 2 3 #2, #3, #6 0 32 2 4 #0, #1, #4, #5 0 332 4 #0, #1, #4, #5 1 34 2 4 #2, #3, #6, #7 0 35 Reserved . . . . . . 63Reserved

In Table 84, bit values may be out of order, but messages included inTable 16 may be identical. Detailed content thereof ma follow contentsof FIGS. 22 to 26 and Tables 70 to 73, and 83.

In Table 84, a DMRS antenna port corresponding to a Comb pattern A and aComb pattern B are as follows.

In case of a first DMRS configuration type using one symbol, DMRSantenna ports corresponding to a Comb pattern A are #0 and #1, DMRSantenna ports corresponding to a Comb pattern B are #2 and #3.

In case of a first DMRS configuration type using two symbols, DMRSantenna ports corresponding to a Comb pattern A are #0, #1, #4, and #5,DMRS antenna ports corresponding to a Comb pattern B are #2, #3, #6, and#7.

Herein, a Comb pattern group is configured with antenna ports using thesame RE pattern. The antenna ports may share the same RE resources, maybe classified into CS values or FD-OCCs or both, and may be defined as aCDM group as like as a second DMRS configuration pattern.

Table 85 below shows cases of indicating two codewords (codeword 0 andcodeword 1 are used) for a first DMRS configuration type.

TABLE 85 Type of Bit Number of Number of Antenna port Co-scheduled valueSymbol(s) layer(s) number CDM group(s) 0 2 5 #0, #1, 0 #2, #3, #6 1 2 6#0, #1, #4, 0 #2, #3, #6 2 2 7 #0, #1, #4, 0 #2, #3, #6, #7 3 2 8 #0,#1, #4, #5, 0 #2, #3, #6, #7 4 Reserved . . . . . . 63  Reserved

In Table 85, bit values may be out of order, but messages included inTable 85 may be identical. Detailed content thereof may follow contentof FIGS. 22 to 26 and Tables 70 to 76, and 83.

Table 86 below shows cases of indicating one codeword (codeword 0 isused and codeword 1 is not used) for a second DMRS configuration type.

TABLE 86 Type of Bit Number of Number of Antenna port Co-scheduled valueSymbol(s) layer(s) number CDM group(s) 0 1 1 #0 0 1 1 1 #0 1 2 1 1 #1 03 1 1 #1 1 4 1 1 #2 0 5 1 1 #2 1 0 1 1 #3 1 1 1 #3 0 1 1 #4 0 1 1 #5 0 12 #0, #1 11 1 2 #0, #1 1 12 1 2 #2, #3 0 13 1 2 #2, #3 1 14 1 2 #4, #5 015 1 3 #0, #1, #2 0 16 1 3 #0, #1, #2 1 17 1 3 #3, #4, #5 0 18 1 4 #0,#1, #2, #3 0 19 1 4 #0, #1, #2, #3 1 20 2 1 #0 0 21 2 1 #0 1 22 2 1 #1 023 2 1 #1 1 24 2 1 #2 0 25 2 1 #2 1 26 2 1 #3 0 27 2 1 #3 1 28 2 1 #4 029 2 1 #5 0 30 2 1 #6 0 31 2 1 #6 1 32 2 1 #7 0 33 2 1 #7 1 34 2 1 #8 035 2 1 #8 1 36 2 1 #9 0 37 2 1 #9 1 38 2 1 #10  0 39 2 1 #11  0 40 2 2#0, #1 0 41 2 2 #0, #1 1 42 2 2 #2, #3 0 43 2 2 #2, #3 1 44 2 2 #4, #5 045 2 2 #6, #7 0 46 2 2 #6, #7 1 47 2 2 #8, #9 0 48 2 2 #8, #9 1 49 2 2#10, #11 0 50 2 3 #0, #1, #6 0 51 2 3 #0, #1, #6 1 52 2 3 #2, #3, #8 053 2 3 #2, #3, #8 1 54 2 3  #4, #5, #10 0 55 2 3  #7, #9, #11 0 56 2 4#0, #1, #6, #7 0 57 2 4 #0, #1, #6, #7 1 58 2 4 #2, #3, #8, #9 0 59 2 4#2, #3, #8, #9 1 60 2 4  #4, #5, #10, #11 0 61 Reserved 62 Reserved 63Reserved

In Table 86, bit values may be out of order, but messages included inTable 18 may be identical. Detailed content thereof may follow contentof FIGS. 2 to 6 and Tables 2 to 5, and 15.

In Table 86, a DMRS antenna port corresponding to a CDM group A, a CDMgroup B, and a CDM group C is as follows.

In case of a second DMRS configuration type using one symbol, DMRSantenna ports corresponding to a CDM group A are #0 and #1, DMRS antennaports corresponding to a CDM group B are #2 and #3, and DMRS antennaports corresponding to a CDM group C are #4 and #5.

In case of a second DMRS configuration type using two symbols, DMRSantenna ports corresponding to a CDM group A are #0, #1, #6, and #7,DMRS antenna ports corresponding to a CDM group B are #2, #3, #8, and#9, and DMRS antenna ports corresponding to a CDM group C are #4, #5,#10, and #11.

Herein, a CDM group may be configured with antenna ports using the sameRE pattern. The antenna ports may share the same RE resources, and maybe classified into FD-OCCs or FD-OCCs or both.

Table 87 below shows cases of indicate two codewords (codeword 0 andcodeword 1 are used) for a second DMRS configuration type.

TABLE 87 (Number of) Bit Number of Number of Antenna port Co-scheduledvalue Symbol(s) layer(s) number CDM group(s) 0 1 5 #0, #1, 0 #2, #3, #41 1 6 #0, #1, #2, 0 #3, #4, #5 2 2 5 #0, #1, 0 #2, #3, #8 3 2 6 #0, #1,#6, 0 #2, #3, #8 4 2 7 #0, #1, #6, 0 #2, #3, #8, #9 5 2 8 #0, #1, #6, #70 #2, #3, #8, #9 6 Reserved . . . . . . 127  Reserved

In Table 87, bit values may be out of order, but messages included inTable 19 may be identical. Detailed content thereof may follow contentof FIGS. 22 to 26 and Tables 70 to 73, and 83.

FIG. 27 is a view showing a method of transmitting a downlink DMRS in anembodiment of the present invention.

Referring to FIG. 27, for a downlink case, in step S2710, the basestation may determine a DMRS configuration type of a DMRS (DL DMRS) tobe transmitted to the terminal among a first DMRS configuration type anda second DMRS configuration type. In step S2720, the base station maytransmit to the terminal information of the determined DMRSconfiguration type by using high layer signaling such as radio resourcecontrol (RRC). In addition, in step S2730, the base station maydetermine a number layers, an antenna port number, a number of symbols,and CDM group(s) used according to an MU-MIMO of the DMRS to betransmitted to the terminal within the determined DMRS configurationtype. In step S2730, the base station may transmit the same to theterminal by using DCI. Herein, the base station may configure the DCIaccording to at least one specific rule mentioned in Tables 69 to 879.

Then, in step S2750, the base station configures a downlink DMRS basedon information of the determined DMR configuration type, and informationof the number layers, antenna port number, the number of symbols, theCDM group(s) used according to an MU-MIMO which are determined withinthe determined DMRS configuration type. Then, in step S2760, the basestation may transmit the configured downlink DMRS to the terminal.

Herein, in step S2770, the terminal may check the DMRS configurationtype of the DMRS received from the base station by using an RRC messagereceived from the base station, configure s DMRS based on theinformation of the number layers, the antenna port number, the number ofsymbols, and the co-scheduled CDM group of the DMRS transmitted from thebase station within the DMRS configuration type by using DCI receivedfrom the base station, and estimate a channel by comparing theconfigured DMRS with the DMRS received from the base station.

FIG. 28 is a view showing a method of transmitting an uplink DMRS in anembodiment of the present invention.

Referring to FIG. 28, for an uplink case, in step S2810, the basestation may determine a DMRS configuration type of a DMRS (UL DMRS) tobe transmitted from the terminal to the base station among a first DMRSconfiguration type and a second DMRS configuration type. In step S2820,the based terminal may transmit to the terminal information of the DMRSconfiguration type by using high layer signaling such as RRC. Inaddition, in step S2830, the base station may determine a number layers,an antenna port number, a number of symbols, and a CDM group(s) usedaccording to an MU-MIMO of a DMRS to be transmitted from the terminal tothe base station within the determined DMRS configuration type. In stepS2840, the base station may transmit the same to the terminal by usingDCI.

In step S2850, the terminal may check the DMRS configuration type of theDMRS to be transmitted to the base station by using an RRC messagereceived from the base station, configure a DMRS based on information ofthe number layers, the antenna port number, the number of symbols, andthe co-scheduled CDM group of the DMRS to be transmitted to the basestation within the DMRS configuration type by using and checking DCIreceived from the base station. In step S860, the terminal may transmitthe configured DMRS to the base station.

Then, in step S2870, the base station may configure a DMRS according tothe information, and estimate a channel by comparing the configured DMRSwith the DMRS transmitted from the terminal.

FIG. 29 is a view showing a block diagram of a wireless communicationsystem according to an embodiment of the present invention.

Referring to FIG. 29, the wireless communication system according to thepresent invention includes a base station 2900 and a terminal 2950.

The base station 2900 includes a processor 2905, a radio frequency (RF)unit 2910, and a memory 2915. The memory 2915 is connected to theprocessor 905 and stores various types of information for operating theprocessor 2905. The RF unit 2910 is connected to the processor 2905, andtransmits or receives or both a wireless signal. For example, the RFunit 2910 may transmit a downlink signal including information of a DMRSconfiguration described in the present description, or may transmit aDMRS configured according to the same. In addition, the RF unit 2910 mayreceive an uplink DMRS from the terminal 2950.

The processor 2905 implements at least one of a function, a process, anda method which is purposed in the present description. In detail, theprocessor 2905 may control such that operations of the base station 2900described above to be performed.

For example, the processor 2905 may include a DMRS configuration typedetermining unit 2906, a DCI information generating unit 2907, and achannel estimating unit 2908.

The DMRS configuration type determining unit 2906 may determine a DMRSconfiguration type used for the terminal 2950 among a first DMRSconfiguration type and a second DMRS configuration type.

The DCI information generating unit 2907 may determine a number layers,an antenna port number, a number of symbols, and a CDM group(s)according to an MU-MIMO of a DMRS to be transmitted to the terminal 2950or received from the terminal within the DMRS configuration typedetermined in the DMRS configuration type determining unit 2906. Forthis, the DCI information generating unit 2907 may use at least one ofthe mentioned specific rules through Tables 69 to 87 described in thepresent description.

The channel estimating unit 2908 may estimate a channel by comparing theDMRS configured based on information determined in the DMRSconfiguration type determining unit 906 and the DCI informationgenerating unit 2907 with a DMRS (UL DMRS) received through the RF unit2910.

The memory 2915 may store at least one piece of information of Tables 69to 87 described in the present description, and provide to the processor905 the information according to a request of the processor 2905.

The terminal 2950 includes an RF unit 2955, a processor 2960, and amemory 2965. The memory 2965 is connected to the processor 2960 andstores various types of information for operating the processor 2960.The RF unit 2955 is connected to the processor 2960 and transmits orreceives or both a wireless signal. The processor 2960 implements atleast one of a function, a process, and a method which is purposed inthe present description. In the above described embodiment, operationsof the terminal 2950 may be implemented by the processor 2960. Theprocessor 2960 may configure a DMRS according to DMRS informationreceived from the base station 2900, and estimate a channel.

In one embodiment, the processor 2960 may include a DMRS configurationchecking unit 2961, a DMRS configuration unit 962, and a channelestimating unit 2963.

The DMRS configuration checking unit 961 may check a DMRS configurationapplied to the terminal 2950 by using a RRC message or DCI received fromthe base station 2900.

The DMRS configuration unit 2962 may configure a DMRS to be transmittedbased on information checked in the DMRS configuration checking unit2961.

The channel estimating unit 2963 may estimate a channel by comparing theDMRS configured based on the information checked in the DMRSconfiguration checking unit 961 with the DMRS received from the basestation 2900.

The descriptions provided in the embodiments of a method of transmittinga DMRS, wherein the method transmits a demodulation reference signal(DMRS) from a wireless communication system to a terminal.

The method may further comprise determining a DMRS configuration type ofa DMRS to be transmitted to the terminal among a plurality of DMRSconfiguration types; transmitting information of the determined DMRSconfiguration type to the terminal by using high layer signaling;determining a number of layers, an antenna port number, a number ofsymbols, and a code division multiplexing (CDM) group according to anMU-MIMO of the DMRS to be transmitted to the terminal within thedetermined DMRS configuration type, and transmitting the determinedinformation to the terminal; and configuring the DMRS according to thedetermined information and transmitting the configured DMRS to theterminal.

An example method of indicating a DMRS layer, and antenna port, andrate-matching in a wireless communication system and an apparatus may beshown. For example, a method of transmitting a demodulation referencesignal (DMRS) from the wireless communication system to a terminal mayinclude: determining a DMRS configuration type of a DMRS to betransmitted to the terminal among a plurality of DMRS configurationtypes; transmitting information of the determined DMRS configurationtype to the terminal by using high layer signaling; determining a numberof layers, an antenna port number, a number of symbols, and a codedivision multiplexing (CDM) group according to an MU-MIMO of the DMRS tobe transmitted to the terminal within the determined DMRS configurationtype, and transmitting the determined information to the terminal; andconfiguring the DMRS according to the determined information andtransmitting the configured DMRS to the terminal.

In the exemplary system described above, processes are described as aseries of steps or blocks based on a flowchart, aspects of the presentinvention are not limited to the illustrated order or sequence. Somesteps may be processed in a different order or may be processedsubstantially simultaneously. Further, it will be understood that theillustrated steps in a flowchart do not necessarily exclude other steps,other steps may be included and one or more steps in a flowchart may beomitted without departing from the spirit and scope of the presentinvention.

The above description is to explain the technical aspects of exemplaryembodiments of the present invention, and it will be apparent to thoseskills in the art that modifications and variations can be made withoutdeparting from the spirit and scope of the present invention. Thus, itis intended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

The processors may include an application-specific integrated circuit(ASIC), another chipset, a logic circuit, and/or a data processingdevice. The memories may include a Read-Only Memory (ROM), a RandomAccess Memory (RAM), a flash memory, a memory card, a storage mediumand/or another storage device. The RF units may include a basebandcircuit for processing a wireless signal. When an embodiment is embodiedas software, the described scheme may be embodied as a module (process,function, or the like) that executes the described function. The modulemay be stored in a memory, and may be executed by a processor. Thememory may be disposed inside or outside the processor, and may beconnected to the processor through various well-known means.

In the described exemplary system, although methods are described basedon a flowchart as a series of steps or blocks, aspects of the presentinvention are not limited to the sequence of the steps and a step may beexecuted in a different order or may be executed in parallel withanother step. In addition, it is apparent to those skilled in the artthat the steps in the flowchart are not exclusive, and another step maybe included or one or more steps of the flowchart may be omitted withoutaffecting the scope of the present invention.

What is claimed is:
 1. A method of transmitting a reference signal, themethod comprising: determining a first set of antenna ports for ademodulation reference signal (DM-RS) transmission; determining, basedon the first set, a frequency index associated with four adjacentresource elements, wherein the four adjacent resource elementscorrespond to two adjacent symbols in a time axis and to two adjacentsubcarriers in a frequency axis; generating, based on a first orthogonalcover code and a second orthogonal cover code, a DM-RS associated withthe first set of antenna ports; and transmitting, via a mapping to thefour adjacent resource elements, the DM-RS associated with the first setof antenna ports.
 2. The method of claim 1, wherein the first orthogonalcover code is associated with the two adjacent subcarriers, and whereinthe second orthogonal cover code is associated with the two adjacentsymbols.
 3. The method of claim 1, further comprising: determining threecode division multiplexing (CDM) groups each comprising four differentantenna ports, wherein a first CDM group, of the three CDM groups,comprises the first set of antenna ports.
 4. The method of claim 3,further comprising: determining a second set of antenna ports for aDM-RS transmission; determining, based on the second set, a frequencyindex associated with additional four adjacent resource elements,wherein the additional four adjacent resource elements correspond to thetwo adjacent symbols in the time axis and to additional two adjacentsubcarriers in the frequency axis; generating, based on the firstorthogonal cover code and the second orthogonal cover code, a DM-RSassociated with the second set of antenna ports; and transmitting, via amapping to the additional four adjacent resource elements, the DM-RSassociated with the second set of antenna ports.
 5. The method of claim4, wherein the first orthogonal cover code is a length-2 orthogonalcover code and is associated with the two adjacent subcarriers, andwherein the second orthogonal cover code is a length-2 orthogonal covercode and is associated with the two adjacent symbols.
 6. The method ofclaim 5, wherein the four adjacent resource elements comprises a firstresource element having a symbol index x and a subcarrier index y, asecond resource element having a symbol index x and a subcarrier index(y+1), a third resource element having a symbol index (x+1) and asubcarrier index y, and a fourth resource element having a symbol index(x+1) and a subcarrier index (y+1) where x and y are positive integers,and wherein a sequence of four orthogonal cover code values for thefirst resource element, the second resource element, the third resourceelement, and the fourth resource element is differently determined foreach antenna port in the first set.
 7. The method of claim 4, furthercomprising: determining a third set of antenna ports for a DM-RStransmission; determining, based on the third set, a frequency indexassociated with second additional four adjacent resource elements,wherein the second additional four adjacent resource elements correspondto the two adjacent symbols in the time axis and to second additionaltwo adjacent subcarriers in the frequency axis; generating, based on thefirst orthogonal cover code and the second orthogonal cover code, aDM-RS associated with the third set of antenna ports; and transmitting,via a mapping to the second additional four adjacent resource elements,the DM-RS associated with the third set of antenna ports.
 8. The methodof claim 1, further comprising: determining to transmit DM-RS viaadditional two adjacent symbols; determining, based on the first set,the frequency index associated with additional four adjacent resourceelements, wherein the additional four adjacent resource elementscorrespond to the additional two adjacent symbols in the time axis andto the two adjacent subcarriers in the frequency axis; and transmitting,via a mapping to the additional four adjacent resource elements, a DM-RSassociated with the first set of antenna ports, wherein at least onesymbol exists between the two adjacent symbols and the additional twoadjacent symbols, and wherein the two adjacent symbols and theadditional two adjacent symbols are comprised in one slot.
 9. The methodof claim 1, wherein the DM-RS associated with the first set of antennaports comprises a DM-RS for a physical downlink shared channel (PDSCH),and wherein the transmitting the DM-RS associated with the first set ofantenna ports comprises transmitting, from a base station and to a userequipment, the DM-RS associated with the first set of antenna ports. 10.The method of claim 1, wherein the DM-RS associated with the first setof antenna ports comprises a DM-RS for a physical sidelink sharedchannel (PSSCH), and wherein the transmitting the DM-RS associated withthe first set of antenna ports comprises transmitting, from a userequipment and to another user equipment, the DM-RS associated with thefirst set of antenna ports.
 11. The method of claim 1, wherein the DM-RSassociated with the first set of antenna ports comprises a DM-RS for aphysical uplink shared channel (PUSCH), and wherein the transmitting theDM-RS associated with the first set of antenna ports comprisestransmitting, from a user equipment and to a base station, the DM-RSassociated with the first set of antenna ports.
 12. A method of mappinga reference signal, the method comprising: determining, by a basestation, a type of demodulation reference signal (DM-RS) configuration;determining two adjacent orthogonal frequency division multiplexing(OFDM) symbols for mapping DM-RSs for at least three code divisionmultiplexing (CDM) groups; determining a first set of antenna ports fora demodulation reference signal (DM-RS) transmission to a first userequipment (UE), wherein a first CDM group, among the at least three CDMgroups, comprises the first set of antenna ports; determining, based onthe first set, a frequency index associated with first four adjacentresource elements, wherein the first four adjacent resource elementscorrespond to the two adjacent OFDM symbols in a time axis and to firsttwo adjacent subcarriers in a frequency axis; and mapping, based on afirst orthogonal cover code and a second orthogonal cover code, a firstDM-RS to the first four adjacent resource elements, wherein the firstDM-RS is associated with the first set of antenna ports.
 13. The methodof claim 12, further comprising: determining a second set of antennaports for a DM-RS transmission to a second UE, wherein a second CDMgroup, among the at least three CDM groups, comprises the second set ofantenna ports; determining, based on the second set, a frequency indexassociated with second four adjacent resource elements, wherein thesecond four adjacent resource elements correspond to the two adjacentOFDM symbols in the time axis and to second two adjacent subcarriers inthe frequency axis; and mapping, based on the first orthogonal covercode and the second orthogonal cover code, a second DM-RS to the secondfour adjacent resource elements, wherein the second DM-RS is associatedwith the second set of antenna ports.
 14. The method of claim 12,further comprising: determining a second set of antenna ports for aDM-RS transmission to the first UE, wherein a second CDM group, amongthe at least three CDM groups, comprises the second set of antennaports; determining, based on the second set, a frequency indexassociated with second four adjacent resource elements, wherein thesecond four adjacent resource elements correspond to the two adjacentOFDM symbols in the time axis and to second two adjacent subcarriers inthe frequency axis; and mapping, based on the first orthogonal covercode and the second orthogonal cover code, a second DM-RS to the secondfour adjacent resource elements, wherein the second DM-RS is associatedwith the second set of antenna ports.
 15. The method of claim 14,wherein the first set of antenna ports comprises one to four antennaports not comprised in the second CDM group or a third CDM group of theat least three CDM groups, and wherein the second set of antenna portscomprises one to four antenna ports not comprised in the first CDM groupor the third CDM group.
 16. The method of claim 15, wherein antennaports in the second CDM group are configured to be selected for a DM-RStransmission after selecting at least one antenna port, from the firstCDM group, for a DM-RS transmission, and wherein antenna ports in thethird CDM group are configured to be selected for a DM-RS transmissionafter selecting at least one antenna port, from the second CDM group,for a DM-RS transmission.
 17. A method of transmitting a referencesignal, the method comprising: receiving, by a user equipment (UE) andfrom a base station, a type of demodulation reference signal (DM-RS)configuration, a first set of antenna ports for a DM-RS transmissionfrom the UE, and information indicating a quantity of code divisionmultiplexing (CDM) groups scheduled for a DM-RS transmission;determining two adjacent symbols for mapping a DM-RS; determining, basedon the first set, a frequency index associated with first four adjacentresource elements, wherein the first four adjacent resource elementscorrespond to the two adjacent symbols in a time axis and to first twoadjacent subcarriers in a frequency axis; generating, based on a firstorthogonal cover code and a second orthogonal cover code, a DM-RSassociated with the first set of antenna ports; and transmitting, via amapping to the first four adjacent resource elements, the DM-RSassociated with the first set of antenna ports.
 18. The method of claim17, further comprising: determining, based on the information indicatinga quantity of CDM groups scheduled for a DM-RS transmission, whether tomap a physical uplink shared channel (PUSCH) to second four adjacentresource elements, wherein the second four adjacent resource elementscorrespond to the two adjacent symbols in the time axis and to secondtwo adjacent subcarriers in a frequency axis.
 19. The method of claim18, wherein a first CDM group, among three CDM groups, comprises thefirst set of antenna ports, wherein antenna ports in a second CDM group,among the three CDM groups, are configured to be selected for a DM-RStransmission after selecting at least one antenna port, from the firstCDM group, for a DM-RS transmission, and wherein antenna ports in athird CDM group, among the three CDM groups, are configured to beselected for a DM-RS transmission after selecting at least one antennaport, from the second CDM group, for a DM-RS transmission.
 20. Themethod of claim 19, further comprising: determining that the quantity ofCDM groups scheduled for a DM-RS transmission corresponds to two orthree, wherein the determining whether to map the PUSCH to second fouradjacent resource elements comprises: determining not to map the PUSCHto the second four adjacent resource elements.